June 2009 Archives

The coolest late June air mass in decades spills over into Wednesday, but it is to loosen its grip on the area later this week in time for the 4th of July holiday weekend. The abnormally cool 65-degree high predicted Wednesday would deliver the Chicago area its coolest July opening in 79-years--since a 65-degree reading in 1930. A temperature at that level at this point in the season is more typical of early May and 18 degrees below normal for the date. It comes on the heels of the coolest June close in 23 years. Clouds and northwest winds were so pervasive that highs struggled to reach 66 at O'Hare International Airport. Northern Wisconsin and Upper Michigan highs failed to make it out the 50s. Rockford's 65 degree high Tuesday broke a record for the coolest June 30.

Cloudiest June in 4 decades

June 2009, which ended at midnight, closed as the Chicago area's cloudiest in the four decades since 1969, having only 51 percent of its possible sunshine. A typical June sees 68 percent.
 

Dear Tom,
As a kid in New Jersey, I cannot recall hearing about tornadoes, but in Chicago we hear about them. Does the Atlantic Ocean reduce the tornado threat?
Andy Charen

Dear Andy,
Your question lacks a definitive answer. The conditions that generate tornado-producing thunderstorms depend upon a proper union of atmospheric and terrain components. Those conditions are satisfied most completely in the so-called "tornado alley" of the Great Plains, and the tornado threat diminishes with increasing distance from that region.

However, local features also affect tornado frequency. Cool air from Lake Michigan usually weakens thunderstorms, but the lake breeze "cold front" sometimes strengthens them, as does the Atlantic Ocean sea breeze front. New Jersey, far from tornado alley, usually lacks other atmospheric conditions conducive to severe weather.

After three days in a row last week with highs in the mid 90s we cool off this week.  The highs expected here over the next two days are more like May highs than late June.  We should get close to 70 today and stay only in the upper 60s tomorrow.

Whether you see the fireworks on the 3rd or 4th of July, it looks like it should be dry and it should be warmer. The forecast calls for a mix of sun and clouds and highs in the lower 80s.

To see how past July 4th holidays have shaped up, click here.

 

Photo courtesy of the Chicago Tribune.

A mass of cool air more typical of May than late June is in firm control of Chicago's weather and appears to have the area headed for one the coolest July openings in 79 years. While temperatures struggle to a high of 70 Tuesday, the predicted 67-degree high Wednesday would make it the city's coolest July 1 since a 65-degree reading in 1930.
The temperature pullback is in dramatic contrast to last week's heat and humidity, which featured a string of three 94-degree highs. The cool pool of air is of Canadian origin, with a faster than normal vertical temperature decline. Such air masses are said to be "unstable" because milder air remains buoyant as it ascends into the chilly air aloft. It's a process that may produce widely scattered light showers Tuesday and Wednesday.

Quiet to the north

Not a single report of severe weather occurred in May and June across northeast Wisconsin north into Upper Michigan. It's the first time that's happened since severe weather records started there 30 years ago.

Dear Tom,
How can it rain for four or five days as it has at times this year? At some point doesn't the atmosphere in any local geographical area become depleted of moisture until evaporation can replace it?
Rob Neufeld

Dear Rob,
The total amount of water evaporated in a column of air above a location is known as precipitable water. It is the amount of water that would fall to the surface if all the water vapor in the atmosphere above that spot condensed and fell as rain.

A precipitable water value of 2.00 inches is exceptionally high and rarely occurs in the Midwest. Nevertheless, rain totals far greater than 2.00 inches occur quite often. This implies that moisture, carried by wind, moves to the location at which rain is falling and continuously re-supplies the rain-producing mechanism (such as a thunderstorm). And that is exactly what occurs in heavy rain events.
 

With Arizona's monsoon season underway (it runs from June 15 through Sept. 15), Gary Wojton, who taught in the Chicago Public School system for years moved to Arizona from Des Plaines 13 years ago, sends us these spectacular photos of towering cumulonimbus. He tells us,
 
"I live in Fountain Hills and am privy to seeing the monsoon clouds form---but barely get rain here in the desert region."
 
Fantastic shots, Gary!! Thanks so much for sharing them---and stay cool in that Arizona heat!
 
Tom Skilling


 
Photos courtesy of Gary Wojton, Arizona

This Sunday thunderstorm in Wasilla,about 40 miles north of Anchorage,covered the ground with hail.Thunderstorms of this intensity aren't everyday occurrences in south-central Alaska--and hail isn't common either. But that's just what happened yesterday and these pictures, taken by Mark Chryson from his front yard, allow us to see just what happened. Mark's pictures were relayed to us by Carolyn Szepanski---and we want to thank both Mark and Carolyn for sharing them with us. They are GREAT shots!  By the way, it's worth noting that there were patches of fog which formed over some of the hail-covered surface.
 
Tom Skilling





Pictures courtesy of Mark Chryson, Wasilla, Alaska
 

Dear Tom,
I remember June 13th as a very stormy and rainy day in the Chicago area. It rained again this year. How often has the Chicago area had rain or storms on this date?
Bill Ooms, Alsip
Dear Bill,
A check of Chicago's precipitation records (1871-2009) on June 13 confirms your suspicions. At least some rain has fallen on that date 78 times out of a possible 139 days, and that computes to rain on 56 percent of the days. The normal mid-June precipitation frequency is 35 percent.
June 13 is also infamous in Chicago weather history. In 1976, a devastating F4 tornado killed two and injured 20 as it carved a "J"-shaped path of destruction through Lemont. The twister tossed cars through the air and destroyed an eight-block area that included half of the Lemont High School. The storm dropped 2-inch diameter hail and flooding rains that totaled 7.5 inches in the Oak lawn area.

Much drier and cooler air follows the thunderstorm-producing cold front that passed through
Chicago overnight. Severe thunderstorm warnings were issued for counties west of the metro
area with a 70 m.p.h gust reported in Franklin Grove, Lee County and 60+ m.p.h. gusts
reported at Ottawa, Mendota, and Earlville in LaSalle County. A strong low pressure center is
forecast to develop and intensify over the eastern Great Lakes early this week with the
resulting northwest flow pulling much colder air into the western Great lakes and Midwest.
Clouds associated with the low will spread out far to the west, covering most of northern
Illinois as well as a good portion of Wisconsin, Michigan and Indiana. Showers, perhaps even
a few thunderstorms are possible both Monday and Tuesday under this unseasonable setup
which should see high temperatures some 10 to 15 degrees below normal.

Warmer, closer-to-normal readings later in the week

As the low pressure system slowly moves northeast, clouds will break and temperatures are
expected to slowly modify later in the workweek.

Dear Tom,
Instead of rising, why does smoke from a chimney descend before a storm?
--Hilary Schnadt

Dear Hilary,
"When the smoke goes low, there will be a blow," and there is some truth to that proverb. In calm, dry weather, hot air from a chimney continues to ascend as long as its temperature is higher than that of the surrounding air. This is more pronounced during cool weather when the hot chimney air is most buoyant. The opposite situation prevails when a rain bearing low-pressure system approaches. Southerly winds ahead of the system bring higher temperatures and humidity. The warmer temperature weakens the current of hot air and, in addition, the smoke particles absorb moisture, become heavier and sink. A drooping smoke plume thus indicates warmer, damper weather and an approaching storm. 

Friday's break in the three-day string of 94-degree highs Chicago area residents sweltered through Tuesday, Wednesday and Thursday, ends briefly Saturday afternoon and evening when a resurgence of heat is expected to result in the week's fourth 90-degree-plus high--and set the stage for potentially powerful thunderstorms expected to hit with a cold front Saturday night.

Friday's official 86-degree high at O'Hare International Airport occurred at 11:29 a.m. before readings declined slowly through the afternoon as northeast winds delivered cooler air.

Perhaps even more significant was Friday's humidity pullback. Dew points--a measure of atmospheric moisture--dropped 15 degrees from the low 70s Thursday to the mid-50s late Friday.

Changes ahead
Big weather changes loom--including the threat of potentially severe storms Saturday night--as
temperatures fall to the low to mid-80s Sunday then the low to mid-70s Monday and Tuesday.

Dear Tom,
What causes heat lightning?
Mike Murphy, Chicago
Dear Mike,
Heat lightning is nothing more than ordinary lightning produced by a distant thunderstorm too far away for the thunder to be heard. With summer thunderstorms routinely building to heights in excess of 50,000 feet, lightning from these storms can be visible at distances beyond 125 miles to anyone with a clear view of the horizon. In contrast, the sound of thunder can rarely be heard beyond a distance of about 15 miles. In fact, the parent thunderstorm cloud producing the lightning may actually be below the horizon, but due to the curvature of the Earth's surface, flashes emanating from the upper levels of the cloud are visible. The term heat lightning came into use because people spent time outdoors on hot, humid summer evenings and were able to view the distant lightning.

The first break in the heat and humidity of the past three days rides into the city on northeast winds Friday.

The air's moisture content retreats from levels more typical of the Gulf of Mexico to those more more closely identified with the Midwest's North Woods region.

Thursday's 94-degree high was the third in as many days, making the three-day spell Chicago's hottest in nearly three years.Only two other occasions since temperature readings have been taken at O'Hare International Airport have highs as warm or warmer than those observed the past three days occurred this early in the summer.

State of the lake
Lake temperatures have warmed to 2009's warmest levels. Satellite estimates of Lake Michigan's average surface temperature now stand at 68 degrees. And the U.S. Army Corps of Engineers reported Thursday that lake water levels are 10 inches higher than a year ago.

Thursday evening threat fizzles under "nose" of powerful jet stream
Heat and humidity as high as Thursday's typically facilitate thunderstorm formation.  But area residents caught a break Thursday. Thunderstorms to the city's north and west--including one with 62 m.p.h. gusts at Whitewater, Wisconsin, dissipated as they moved in Chicago's direction, once they encountered storm-extinguishing sinking air beneath the nose of a pocket of
powerful jet stream winds.

Dear Tom,
I remember a June 11 back in the late 60s or early 70s with a killing frost that wiped out most of my garden. Details?
Jim Marrone Lake Bluff
 
Dear Jim,
The very cold morning in the Chicago area that you remember was on June 11, 1972. In the city, the then official Midway Airport site logged a record low of 41 degrees (since tied in 1980), but the real chill was out in the suburbs where readings dropped into the lower and middle 30s. The morning's coldest temperature was logged in northwest suburban Marengo, a frosty 29 degrees. Other suburban lows that morning included Antioch, 33; Aurora 35; Barrington 30; Waukegan 34; Joliet 35; and Park Forest. 36.

The warming effect of the city's heat island and Lake Michigan was evident from the 46 degrees registered at the site in Grant Park near Buckingham Fountain. 
 
 

Dear Tom,
I remember a June 11 back in the late 60s or early 70s with a killing frost that wiped out most of my garden. Details?
Jim Marrone Lake Bluff
 
Dear Jim,
The very cold morning in the Chicago area that you remember was on June 11, 1972. In the city, the then official Midway Airport site logged a record low of 41 degrees (since tied in 1980), but the real chill was out in the suburbs where readings dropped into the lower and middle 30s. The morning's coldest temperature was logged in northwest suburban Marengo, a frosty 29 degrees. Other suburban lows that morning included Antioch, 33; Aurora 35; Barrington 30; Waukegan 34; Joliet 35; and Park Forest. 36.

The warming effect of the city's heat island and Lake Michigan was evident from the 46 degrees registered at the site in Grant Park near Buckingham Fountain. 
 
 

Dramatic views from west suburban Elgin of the towering cumulonimbus clouds (thunderheads) which produced Wednesday Cook County downpours, wind and flooding
 
 
Matthew Cumberland of Plano photographed Wednesday's 53,000 ft. tall cumulonimbus clouds from Elgin as thunderstorms pounded sections of Cook County and northwest Indiana, producing flooding deluges, lightning, locally damaging winds and even hail.  Great shot, Matthew--MANY THANKS!!
 
-Tom Skilling

 Photo courtesy of Matthew Cumberland

Thanks to Heriberto Quiroz for this view of Wednesday's powerhouse thunderstorms from Chicago's Pilsen neighborhood. Great shot--THANKS Heriberto!
 
Tom Skilling
 

Photos courtesy of Heriberto Quiroz, Pilsen-Chicago
 

Thunderstorms exploded to life along a narrow 20 mile wide corridor from Cook County southeastward into northwest Indiana midday Wednesday. An inland-moving lake breeze front was the meteorological culprit. It ushered easterly winds off Lake Michigan into a hot, humid air mass dripping with 1.50 inches of evaporated water. The inland racing flow encountered a windless tropical air mass, producing a pile-up of air which was forced to rise and cool.  Thunderstorms soon resulted and towered above 50,000 feet unleashing torrential downpours. As much as 2.12 inches was measured at the Weather Bug rain gauge at Frazier Magnet School in Chicago as 63 m.p.h. winds raked Midway Airport and floodwaters submerged streets and basements in Cicero.  The storms erupted over the same corridor repeatedly between 1 and 3 p.m.---a process referred to as "training." They generated more than 1,700 cloud to ground lightning strokes in just over two hours.
 
 
Heat enters third day Thursday; more storms due
 
Three consecutive 90-degrees have occurred at  this early stage of the summer season in only one of three years at Midway Airport since 1928.

Dear Tom,
Is there such a thing as dry lighting?
Audrey Clark

Dear Audrey,
Dry lightning is a colloquial term for lightning that occurs from a thunderstorm that is not producing precipitation. It's not a meteorological term and its implications are factually incorrect for two reasons.

Lightning, the transient flash of light produced by an electric discharge in the atmosphere (usually in thunderstorms, but also in volcanic ash clouds and, very rarely, in sandstorms) is never wet in the first place.
 
Secondly, thunderstorms always produce precipitation, but rain falling from a storm sometimes falls through a layer of dry air and evaporates before it reaches the ground. This is known as a dry thunderstorm (also technically a misnomer). Such storms occur in the western U.S. in the summer and are the leading natural cause of forest fires.

The Chicago area wasn't alone with thunderstorms Wednesday. Our friend
Mary Anne Best, who regularly keeps us posted on weather conditions 90
miles south of Chicago near Remington, Indiana, shares this dramatic
Wednesday evening shot of a towering complex of thunderstorms which
were occurring 50 to 60 miles southeast of her. Doppler radar scans put
the tops of these storms at 37,000 ft.  Beautiful shot, Mary Ann!!

Tom Skilling

Photos courtesy of Mary Ann Best, Remington, Indiana

Thunderstorms that developed Wednesday afternoon (6/24/09) along a lake breeze front produced damaging winds across the southern half of Cook county.

At Midway Airport, fence and light damage occured on the southeast side of the airfield.  A Southwest Airlines cargo hanger also sustained some wind damage.  In Burbank, two people suffered minor injuries when winds toppled a dugout.  Trees were reported down in Cicero, Burbank, and on the south side of Chicago. 

Some of the top wind gusts include:

63mph   Midway Airport at 1:38PM

58mph   Sauk Village, IL at 1:53PM

55mph   Burbank, IL at 1:56PM

49mph   Chicago Heights, IL at 2:00PM

For a complete recap of this afternoon's storms, check out the WGN Severe Weather Blog at the link below. 

http://weblogs.wgntv.com/chicago-weather/severe-weather/

 

Still another view of Wednesday's bank of towering 50,000+ ft. tall lake breeze-induced thunderheads (cumulonimbus clouds) hovering over Cook County as photographed between 1 and 2:30 p.m. from the Illinois Mathematics and Science Academy in Aurora--some 40 miles west of Chicago--by Matt Piechota who works there.  Spectacular shots, Matt!  Thanks for sharing them with us.

Tom Skilling



 
Photos courtesy of Matt Piechota

Jen Ingram's 10-year old son Sam---an avid weather enthusiast with the dream of becoming a weather forecaster or tornado chaser----snapped these shots of thunderstorms forming east of Donovan, Illinois in downstate Iroquois County.  What a terrific job Sam!  Thanks to both Jen and Sam for sending these along!
 
Tom Skilling

 
 
Photos courtesy of Jen and Sam Ingram, Donovan, Illinois

As viewed from the Geneva Commons on Randall Rd, courtesy of Rob Cannon:

Photo courtesy of Rob Cannon

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The same storms as viewed from Cary, Illinois:

Photos courtesy of Jason Janczak

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As viewed from Wilmington, Illinois:



Photos courtesy of Jenn and Bill in Custer Park, Illinois (south of Wilmington)

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Check out these close-up shots of the thunderstorm towers as taken from suburban Lisle




 Photos courtesy of Mary King, Lisle, Illinois

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Wide view as seen from Sugar Grove
CLICK ON IMAGE FOR FULL SIZE:

Photo courtesy of Roland Muts, Sugar Grove, Illinois

Wednesday's storms banked between 1 and 2 p.m. over Cook County as viewed from west suburban Aurora






 
Photos courtesy of Heather Brinkmann, Aurora, Illinois

Wednesday afternoon's violent lakebreeze-induced  thunderstorms, responsible for 63 mph gusts at Midway Airport, flooding and downed trees and power lines in Cicero and ripping part of a roof off Burbank's St. Lawrence High School while overturning a baseball dugout, producing slight injuries to a coach and player, are shown here from a distance in this spectacular photo taken by Jim Hancock far west suburban Sycamore, Illinois. Sycamore is in DeKalb County approximately  68 miles west of Chicago.  Doppler radar scans put cloud tops at the height of these storms over Cook County (between 1 and 2 pm) at between 43,000 and 53,000 ft.

Dopper rain estimates--which, because of the presence of hail which can corrupt rainfall estimates off current generation Doppler radars---were put at more than 2.50 inches in sections of central Cook County. Veteran weather observer Frank Wachowski reports 0.78 inches fell at Midway Airport---but only 0.07 inches at his home in nearby Burbank. A caller from Cicero reported flooded streets and basements, confirming radar indications the storms' heaviest rains fell there and in a corridor from Oak Lawn to Elmwood Park. He is a 43-year resident of Cicero and says today's storm was among the worst he's seen. Converging low level winds along an inland-moving lake breeze front just after noon Wednesday, set the highly concentrated, flooding storms in motion and allow the thunderstorms to erupt, despite the presence of capping earlier today(comparatively warm air aloft which cuts into the rate at which temperatures fall with height). O'Hare topped out at 94-degrees for a second day.  Weather Bug sensors indicated unofficial highs of 98-degrees at Burr Ridge and  97-degrees as Lemont, Alsip and DeKalb.
 
-Tom Skilling


 
 
Photos courtesy of Jim Hancock, Sycamore, Illinois

Our first heat wave of 2009 has buckled pavement and caused power outages.  Our WeatherBug network registered high temperatures in the triple digits yesterday west of the city.  Today should be just as hot or even hotter.  We are starting off a few degrees warmer because of a deck of clouds that drifted over the city last night.  If those clouds thin enough this morning, we could be looking at topping yesterday's highs and approaching record temperatures this afternoon.

Here are some of the high temperatures recorded on our WeatherBug network yesterday:

102 Westfield Community School, Algonquin

102 Hillcrest Elementary School, Elgin

101 F.E. Peacock Middle School, Itasca

100 Geneva Middle School, Geneva

99 Fremd High School, Palatine

 

For more photos of people beating the heat, check out the Chicago Tribune.

The mercury reached 90 degrees in Chicago for the first time in 2009 at 12:09 p.m. Tuesday on its way to the warmest June high temperature in the city in four years.

The 94-degree high at O'Hare International Airport equaled last summer's hottest temperature.
This year the heat is late to arrive in Chicago. Since 1928 at Midway Airport, an average of five highs of 90 degrees or warmer have occurred by this date.

Heat fuels Iowa storms

Near triple-digit heat in Iowa fueled powerful thunderstorms with cloud tops that towered to 57,000 feet and sent temperatures diving more than 20 degrees while producing 60 m.p.h. wind gusts and numerous reports of large hail.

The storm cluster began Monday evening in Colorado and is the latest in a series to rotate around the periphery of a dome of hot air in what meteorologists refer to as a "ring of fire" pattern.

Dear Tom,
What percent of U.S. tornadoes touchdown west of  the Mississippi River compared to east?
Hank Hartzell  Burlington, Wisc.

Dear Hank,
Based on  average annual tornado data for 1953-2004 from the National Climatic Data Center and the Storm Prediction Center, areas west of the Mississippi River log 62 percent of this nation's twisters as compared to 38 percent in areas to the east. The vast majority of the twisters west of the Mississippi occur in the southern and central Plains from Nebraska to Texas, an area frequently referred to as "Tornado Alley."

With an average of 139 twisters annually Texas dominates all states in tornado activity, followed by Oklahoma with 57 and Kansas and Florida tied with 55.

Illinois ranks second in tornadoes for states east of the Mississippi averaging 35 each year, trailing only Florida with 55.

Michael Frankowski forwards us this beautiful photo of a cloud to ground lightning stroke taken Monday morning near Oregon, Illinois. A wonderful shot, Mike--your photos are always spectacular!  MANY THANKS!!
 
Tom Skilling
 
Photo courtesy of Mike Frankowski, South Elgin, Illinois
 

Thanks to Sara Mickel from Park City, Illinois for sharing this picture of flooding on the Des Plaines River near Wadsworth. Sara comments that the river level has not changed much since Sunday.

The Des Plaines River swollen by this area's recent deluges
 
With the Des Plaines River--and others in the Chicago area---so high in the wake of recent downpours, this photo from Sara Mickel is especially striking. Sara took it where the Des Plaines River passes under the pedestrian bridge at Stirling Lake near Wadsworth. Importantly, she notes the clearance between the bridge and the river hasn't changed much since Sunday and that the new wetland restoration project on Rt. 41 has retained much of the water which would otherwise have flowed into flood zones south of Waukegan! Many thanks for the fantastic photo and for a very timely update, Sara!
-Tom Skilling
 

Photo courtesy of Sara Mickel, Park City, Illinois

The same hot air mass responsible for 89-degree highs Monday-the warmest
temperatures to date in 2009 at O'Hare International and Midway Airports
tightens its grip on the Chicago area Tuesday and Wednesday. Heat
advisories have been hoisted for all but lakeside areas where light
onshore (easterly) afternoon winds should temper highs to the 80s while
90s occur inland. Wednesday may prove to be the hottest of all with heat
indexes approaching a dangerous 106 right up to the lake.
 Monday's heat and humidity in southwestern Iowa reached extreme levels
when the country's highest dew point, 82 degrees, combined with a high
of 93 degrees to produce a 117-degree heat index at Shenandoah, Iowa.
 
Florida heat
After several days of suffocating heat and humidity, Florida is in line
for somewhat cooler weather Tuesday. More temperature records tumbled
Monday with Vero Beach leading the heat parade with a record high of 102
degrees and a heat index of 111.

Dear Tom,
On our wedding day June 20, 1953 it was 104 and on our 35th anniversary in
1988 it was also 104. How often does Chicago's temperature reach 100 on the
same date.
Frank and Vi Jasonowicz Palatine

Dear Frank and Vi,
Since 1871 Chicago's official thermometer has reached triple digits 61
times. There were only a dozen days with two 100 degree highs,  three days
that logged three and just one day, July 10, where the thermometer reached
100 degrees four times. The first time was a high of 102 on July 10, 1901.
The next encounter was during the "Dust Bowl" in 1936 with another 102,
followed by a 100 in 1976 and most recently 101 in 1989. The city has not
logged a 100 degree temperature in nearly four year, the last occurrence was
on July 24, 2005 when the mercury peaked at a sizzling 102.

Thanks to Jack Conarchy for passing on these photos of flooding on this street following the torrential rains Friday night. Jack reported 3 feet of water on his street and unfortunately 6 inches in his basement.

Photos by Jack Conarchy

Get set for a muggy Monday.  High humidity will fuel some isolated thunderstorms today.  Earlier this morning nearly 4 inches of rain fell in the town of Mazon down in Grundy County.  While today's storms may be isolated, the ones that do form will be capable of producing some heavy rain. 

Here are some other rain totals for this Monday from our WeatherBug network:

.63" Morris

.57" McHenry

.49" Naperville

.44" South Elgin

Finally, here is the doppler radar rainfall estimate for the day courtesy of the National Weather Service Office in Romeoville:

As if taking a cue from the calendar, Chicago's weather has finally turned summery and will remain so through the week. It won't be oppressively hot or oppressively humid.
And thunderstorms--an integral component of the warm season around here--will be in and out of the picture through Friday, but the great majority of hours during the five days will be dry.
Chicago sits at the northern edge of hot air to the south, and that air mass will repeatedly splash into the city this week, then retreat slightly.

Southern heat is on
Sweltering summer temperatures and sticky humidity are no strangers to the southern half of the United States in June, July and August. Residents there accept it and deal with it. This year, though, oppressive heat and humidity arrived early and hit hard from Kansas,
Oklahoma and Texas east across the Deep South. Many cities there have been establishing daily high temperature records since early last week, and computer models indicate no significant change to the sultry pattern this week.

Dear Tom,
Can you confirm that there really can be a "green flash," and why it is so rare?
Mac Sims
Dear Mac,
The "green flash" is a brief flash of green light emanating from the upper rim of the rising or setting sun. It occurs because sunlight is bent slightly upward as it passes through the atmosphere, and the bending is greatest when the sun is on the horizon.
Because the shortest wavelengths of sunlight (blues and greens) are bent upward the most, those are the colors that appear first at sunrise and last at sunset. Most of the blue wavelengths are removed by atmospheric scattering, and that leaves green for the flash.
The green flash is seen most often when viewed across the expanse of a large body of water. It requires a nearly perfect combination of clear skies, excellent visibility and atmospheric conditions that enable the air to act as a lens and magnify the flash.

The National Weather Service in Romeoville conducted a storm  damage survery in the Woodstock area in the wake of the severe thunderstorms that raked the region on Friday. They confirmed an EF 1   tornado (on the Enhanced Fujita scale) with top winds of about 100 m.p.h. The twister first hit around 7:10 p.m. near Highway 14 and Davis Road in the south part of Woodstock. The  damage path was three-quarters of a mile long with a maximum width of about 75 yards. The complete National Weather Service report on this storm can be found on their website at www.crh.noaa.gov/lot

 

Matt Hendricks took this neat picture near Riverside, Michigan of the thunderstorms approaching shoreline after crossing the lake.

Photo by Matt Hendricks

Saturday's sunshine gave residents across northern metropolitan Chicago a chance to recover from the flooding rains and damaging winds that swept through the area Friday afternoon. Commonwealth Edison expects power to be fully restored today to all of the 120,000 households that lost electric service. Having dealt with periods of swollen rivers, impassible roads and flooded basements literally since September, 2008, waterlogged Chicagoans are increasingly voicing sentiments like, "Enough, already!" Nothing would please them more than a couple weeks of sunny, rain-free days. 
 
The "Ring of Fire"
 
Unfortunately, an extended period of dry weather is not in the picture. A massive "dome" of very warm, humid air sprawling across the south half of the nation is expected to remain in place for several days. Chicago sits in a turbulent boundary zone at the northern periphery of that heat dome -- within a meteorological "ring of fire" that is a fertile breeding ground for thunderstorms. 

Dear Tom,
What is the difference between a solstice and an equinox?
Todd Flessner

Dear Todd,
 
During the course of a year, four days are noteworthy as the Earth revolves around the sun.
 
The summer solstice occurs around June 21, when the sun is directly overhead at its northernmost latitude (the Tropic of Cancer). It is the first day of astronomical summer and the day with the most daylight in the Northern Hemisphere. The winter solstice, occurring about Dec. 21 (when the direct rays of the sun reach their southernmost position at the Tropic of Capricorn), marks the start of astronomical winter and gives the Northern Hemisphere its least amount of daylight.
 
The equinoxes are the two dates the overhead sun crosses the equator. The vernal equinox, about March 21, marks the onset of spring; the autumnal equinox, about Sept. 21, heralds the start of fall.

Thanks to our many viewers and readers who were kind enough to send us a multitude of pictures depicting many aspects of Friday's day-long bout with severe weather.

 

This shot was taken just west of Rochelle.

 

Photo by Frankie and Jeanne Armstrong

Storm shot taken near Sleepy Hollow

Photo by Ericka Carlson

 

Storms rolling in as seen from Children's Memorial Hospital

Photo by Kelly Conforti

 

Shot of storm approaching Baroda, Michigan

Photo by Jim Wolf

 

Storm approaching Chicago as seen from a site near Navy Pier

Photo by Elaine Karp

 

Storm shot from the west side of Elgin

Photo by David J. Noffs

Lightning shots taken near the lake at Claredon

Photos by Tracey Surface

Storm photo taken in downtown Zion

Photo by Jason Lewis

 

A calming and beautiful rainbow visible from Chicago Heights after a chaotic day of severe weather

Photo by Susan Drechney 

Dear Tom,
What is the difference between a Solstice and an Equinox?
Todd Flessner, Woodridge
Dear Todd,
During the course of the year, four days are noteworthy as the Earth revolves around the sun. The summer solstice occurs around June 21, the date on which the sun is directly overhead at its northernmost latitude, the Tropic of Cancer. It is the first day of astronomical summer and the day with the most daylight in the Northern Hemisphere.
The winter solstice, occurring about December 21, occurs when the direct rays of the sun reach their southernmost position and it marks the start of astronomical winter. It provides the Northern Hemisphere its least amount of daylight.
The equinoxes are the two dates the sun crosses the equator and the length of day and night are about equal at all points on Earth. The vernal equinox occurs about March 21, denoting the start of astronomical spring; the autumnal equinox, about September 21, heralds the start of astronomical autumn.  

From Ben Odean in Chicago. Taken from a rooftop near Division and Western looking northwest and northeast around 10:25am.

 

Jim Wolf, a trained weather spotter in Stevensville, MI., sent us this great shot. Thanks, Jim!

Thanks, Bill!

Elaine Karp took this photo earlier today as the storm was approaching near Navy Pier.

Thanks, Elaine!

Photo by Jim Rook

Photo by Bart

Thanks to Tim and Sue Ryan for these  storm pictures taken this morning in northwest suburban Marengo.

 

Photos by Tim and Sue Ryan

Thanks to Patrick McCarron for sending us this shot as storms approached Carpentersville around 9 a.m. this morning.

Photo by Patrick McCarron 

The atmospheric ingredients for severe thunderstorms --warmth, high humidity, an approaching cold front, a 45-m.p.h. low-level (5,000 feet) jet stream and a vigorous disturbance at higher levels---are falling into place Friday. It's a situation that favors the development of thunderstorms with large hail and damaging outflow winds this afternoon and evening. Heavy rainfall and flash flooding are additional concerns, especially considering
our soggy soils.

Summer arrives, big time

Until now, the temperatures that Chicagoans associate with summer have been sporadic and short-lived. By this time next week, however, summer heat and humidity will have arrived in Chicago, and computer models suggest it will be more than a one- or two-day tease. Rather, the onset of a new and warmer weather regime across the Midwest suggests, for Chicago, a multi-day string of afternoon temperatures near or above 90 degrees, accompanied by uncomfortably high humidity. The timing is appropriate: Summer (astronomical summer) begins on June 21.

Dear Tom,
You have said Havre, Montana, is the US city with the largest temperature difference between its all-time highest and lowest temperatures. What US city has the smallest difference between its highest and lowest temperatures?
Scott Thomas

Dear Scott,

Let's review the statistics. Chicago's all-time high and low temperatures  
are 105 degrees and -27 degrees, respectively, for a spread of 132 degrees.  
Comparable figures for Havre, Montana, are 111 and -57, for a spread of 168  
degrees, a US record.

Honolulu, Hawaii, stands at the other end of the temperature scale, and  
that is the answer to your question. Its all-time highest and lowest  
temperatures are 94 and 53 degrees, for a range of 41 degrees. Honolulu's  
exceptionally moderate climate results from the tempering effect of the  
surrounding Pacific Ocean and a very small seasonal variation in energy  
received from the sun.

Thanks to David Mayhew, a regular contributor of spectacular photos to this blog for passing along these great shots taken on Wednesday in Kansas and Nebraska. More of David's great phots can be seen on his website at www.DavidMayhewPhotography.com

This first photo was taken near the town of Oketa in northeast Kansas. A tornado was reported with this storm, but this shot only shows a dust cloud.

The rest of the photos were taken near dusk in and around Grand Island, Nebraska. They show a nicely defined funnel. The main tornado with this storm traveled along State Highway 34, just north of I-80.   

 

All photos by David Mayhew www.DavidMayhewPhotography.com

 

A dramatic weather pattern shift (for which the Midwest is notorious) is beginning to unfold. The change from a cool, cloudy and rainy weather regime to sunny, hot and humid conditions gets under way Thursday, though it will be a multi-day transition. The Storm Prediction Center advises that a powerful impulse moving across portions of the central and southeastern United States is likely to trigger severe thunderstorms here (and elsewhere in a band from Minnesota to the Carolinas) later today. Storms move out of the Chicago area by Saturday morning and the weekend looks dry.  
 
Warm, muggy days ahead
 
A broad swath of the nation from Oklahoma and Texas east to Georgia has been sweating through 90-degree temperatures and oppressive humidity for several days. That air mass is expanding northward and is due to arrive in Chicago in about a week. And once it gets here, the muggy weather is likely to persist for several days. Beginning one week from today, computer models indicate a string of five to seven days here with afternoon temperatures in the 90s. 

Dear Tom,
Your use of "normal temperatures" and "average temperatures" is confusing. Wouldn't "seasonal" be better than "normal"?
Jim Hurley, Glenview, Ill.
Dear Jim,
Seasonal temperatures refer to readings that occur commonly during a particular season, such as during the spring. The term does not have a precise definition in the atmospheric sciences. Meteorologists define "average" and "normal" in ways that are somewhat different from standard usage, and that is an unfortunate source of confusion.
 
In the atmospheric sciences, an average (such as an average temperature) is just what you think it is -- the sum of all the values in a set divided by the number of values. A normal is different. It is the specific average over a standard 30-year period, currently 1971-2000. For example, a normal temperature is the average temperature over the 30-year period from 1971 through 2000.
 

A few showers may linger into this morning following Tuesday's thunderstorms that unleashed street-flooding rains over far southwest suburban Chicago, and another round of thunderstorms is likely late today into Friday. It's a story that we're getting used to hearing: Those storms could bring locally heavy rain. Looking ahead, an abrupt change signals at least a few 90-degree days by month's end.
 
Where are the mosquitoes?
 
It's a question that we're beginning to hear, prompted by the frequent and heavy rains that we have been enduring this spring. Dave Zazra of the North Shore Mosquito Abatement District says culex mosquitoes (the carriers of West Nile virus) breed in standing water, but our frequent rains have prevented stagnant pools from forming. "If all of a sudden we stopped getting these flushing rainstorms, that could be a problem," he said. Mosquito abatement officials caution that, due to the uncertainty of the weather, it is too early to predict the nature of this mosquito season.
 
 

Dear Tom,
Why are forecasts from "computer models" sometimes in error?
Aaron Turnier
 
Dear Aaron,
Computer models consist of sets of mathematical equations that describe how the atmosphere operates. The equations consider such quantities as temperature, moisture and wind, and how those quantities will change as time (from a few hours to several days) passes.
 
The models have three main sources of error. The first is our incomplete knowledge of atmospheric processes: The equations themselves aren't perfect. Then there are "initialization errors." At the outset, it is impossible to describe the atmosphere perfectly because of lack of data, especially over the oceans. Finally, there are "resolution" problems. Calculations are performed on volumes of air perhaps 20 miles on a side. Weather features (like thunderstorms) smaller than that are not handled very well.

 

Mary Beth Binek sent us this picture taken in Downers Grove with the sun shining through a hole in the clouds. Her husband remarked that it looks like an angel.

Photo by Mary Beth Binek

Thanks to Steve Rayman for passing along these amazing photos taken Monday at Emerson New  Jersey in Bergen County where a freak thunderstorm dropped tons of hail that piled up more then 4" deep. Residents of the area likened the landscape to that of a winter snowstorm. Heavy rainfall also produced flooding.

    

Photos by Ree

It will soon be time to break out the old heat index chart.  The heat and humidity will be building towards the end of this week.  Highs will reach into the middle and upper 80s on Thursday and Friday.   The combination of those warm temperatures and expected higher humidity will make it feel like the 90s.  Remember that the heat index combines the temperature with humidity to give us an idea of what it will feel like.  We are expecting the highest heat index values so far this year by the end of the week.  Here is the heat index chart courtesy of the National Weather Service:

Warm temperatures have been notable in their absence so far this season, a
fact not lost on the area's warm-weather devotees. History tells us that an
average spring delivers about 16 days (Midway Airport data) on which the
high temperature reaches at least 80 degrees by this date, and three days at
or above 90 degrees. Thus far, Midway has logged only nine 80-degree days
and no days in the 90s. That's about to change. Heat and humidity that has
been resident across the south third of the nation for several days is
expanding northward and arrives here in strength later this week.

Kansas battered

Warm, humid and unstable air that extended from the southern Great Plains
east to the Appalachians proved to be a fertile breeding ground for severe
weather in all its manifestations. A tornado near Dodge City, Kansas, was on
the ground for ten minutes late Monday afternoon and another twister struck
near El Dorado. Hail 2.75 inches in diameter bombarded Alta Vista, Kansas,
Monday evening, shattering windows and damaging roofs.

Dear Tom,
Your excellent Tornado Seminar last April left me wondering, what is the worst tornado ever to occur in Illinois?
Jon Palmer

Dear Jon,
It was the Tri-State Tornado of March 18, 1925. Not only does that occurrence stand as Illinois' worst tornado disaster (in terms of human deaths and injuries), it ranks as the worst ever to strike the United States.

Tornado historian Tom Grazulis has written eloquently about the tornado in his book, Significant Tornadoes, describing it as "... the largest, longest, fastest, most destructive and most deadly tornado in U.S. history. In all respects, this remarkable tornado stands in a class of its own."

The Tri-State Tornado cut a continuous 219-mile path from southeast Missouri across southern Illinois into southwest Indiana. Along the way, 695 people died (613 in Illinois) and at least 2,000 were injured.
 

Enjoy today's sunny sky and pleasant temperatures. Those conditions won't last because Chicago's weather pattern is set to be stormy by mid-week.
Two distinct weather systems will be surging across the Midwest in upcoming days. The first arrives with showers and thunderstorms late Tuesday and continues into early Thursday.
Total rain accumulations could exceed 1.5 inches. A second system arrives late Thursday and brings another round of showers and thunderstorms from late Thursday through Friday into Saturday.

The impact of a cold lake
Away from the shore, Lake Michigan water temperatures are now running from 48 degrees to 54 degrees. That's why air blowing off the lake is so chilly at this time of the year. On sunny days with east winds, lake-cooled air warms as it moves inland, typically moderating 10 to 15 degrees by the time it arrives at the Fox Valley. On cloudy days, the moderation is less than
5 degrees.

Dear Tom,
With summer approaching, I am reminded of the wickedly hot summer of 1988 here in Chicago. I had an apartment with no air conditioning then and I suffered. How hot was it?
Allen Katz
Dear Allen,
Hot, very hot -- and dry. In addition to the heat, the spring and summer of 1988 brought severe drought conditions to the Midwest and much of the nation. That also was the summer during which wildfires raged across 36 percent of Yellowstone National Park.
Here in Chicago, the summer was a scorcher. Midway Airport logged 48 days at or above 90 degrees (an all-time record for the city), and eight days at or above 100. With an average temperature of 77.4 degrees, it was Chicago's second hottest summer. The summer's average high temperature, 87.8 degrees, is also a record. Without air conditioning, there is no doubt that you suffered.

After a June that opened with record chill following a spring characterized by clouds, sub-normal temperatures and deluges of rain, Chicagoans increasingly anxious for summery warmth, sunshine and rain-free days must face another meteorological disappointment. A consensus of computer models suggests that below-average temperatures are likely to persist here through the week. In addition, persistent east winds blowing more often than not off the chilly waters of Lake Michigan will keep lakeshore areas especially cool in upcoming days. A good deal of sunshine today and Monday is just a tease. Another storm system is headed toward Chicago and the Midwest.
 
The bad news
 
In a weather situation more reminiscent of January than June, computer models indicate the development of a "closed upper low" over the Midwest. This feature is a large and slow-moving pool of chilly air 15-30 thousand feet aloft, beneath which the weather is mainly cloudy, showery and cool. That system arrives here Tuesday and persists into Saturday.
 

Dear Tom,
Why is the shortest day of the year, Dec. 21, not near the midpoint of the coldest weather of the season; and why is the longest day of the year, June 21, not near the hottest weather of the season?
--Martin Vesole, Highland Park

Dear Martin,
The annual cycle of temperatures lags behind the annual cycle of daylight by about one month---the so-called lag of seasons. Chicago's temperature cycle bottoms in mid-January and peaks in mid-to-late July.  Even though heat input from sunlight increases after Dec. 21, the Earth is still losing more heat to space than it receives and temperatures continue to fall. By mid-January, though, increasing heat gain overcomes the loss and temperatures begin to rise. In the summer, heat gain, declining after June 21, exceeds heat loss until mid-July. 

The cloudy, chilly and rainy open to June here has been the talk of the town. So far this June is running more than 12 degrees cooler than last year, and the clouds, rain and chilly lake winds have been persistent. The average temperature at O'Hare International Airport through Friday has been only 59.5 degrees: nearly 7 degrees below normal and the coldest since records there began 50 years ago.

More bad weather is on the way Saturday with a cold rain expected to linger through the bulk of the morning. Rainfall could be heavy -- especially north of the city, which would be a reversal of Thursday's deluge that targeted the southern suburbs.

Better days ahead
Encouraging signs in recent computer runs signal a change to more typical June weather which by now should feature daily highs around 80 degrees. A return of sunshine should boost temperatures well into the 70s Sunday and Monday, though lake cooling will continue. By midweek a northward shift in the jet stream promises a steady diet of highs in the 80s, though showers and thunderstorms are likely to accompany the warm-up.

Dear Tom,
I work in a high school and found an old picture of the 1930 graduating class on what looked like a warm, windy day. What was it like in Chicago on May 13, 1930?
Nancy Eliason
Dear Nancy,
Your observations were pretty much right on. We had Frank Wachowski check the archives, and he confirmed your inferences. It was a indeed a warm day with the high temperature reaching 75 degrees. After some morning sprinkles, skies cleared to set the stage for a mostly sunny afternoon. Winds were gusty, blowing from the southwest in the morning but from the northwest in the afternoon after the skies cleared. It was a good thing that the picture was taken on May 13. The weather turned chilly after that and did not warm up for more than a week until it reached 85 on May 21.

Enjoy today's dry interlude -- it won't last long: The next storm system is quickly heading this way. Area rivers, swollen with runoff from heavy rains across southern metropolitan Chicago on Thursday, won't have much time to drain before a new round of thunderstorms rolls in Friday night. Rain continues through much of Saturday, but Sunday looks dry. Temperatures continue on the cool side through the weekend and persistent winds off Lake Michigan will keep it especially cool in lakeshore areas.  
 
Looking ahead, a major weather pattern shift is in the works and it signals summery warmth -- finally -- but its effects won't arrive here until the middle of next week. Temperatures well into the 80s are likely by next Wednesday, accompanied, unfortunately,  by humidity that also carries an ongoing threat of thunderstorms. 
 
Thursday's deluge
Thursday's rain was a study in contrasts. Little or no rain fell across the north half of the metropolitan area (only 0.01 inch at O'Hare, for example) and residents there probably wondered what the fuss was about, but torrents of rain struck southern sections and northwest Indiana. Kankakee County in Illinois and Lake and Porter Counties in Indiana were especially hard hit by flash flooding. The rain finally ended late Thursday afternoon.
 

 

Dear Tom,
Is there somewhere relatively near Chicago where one could enjoy a spectacular view of the stars of the Milky Way, without the interference of nearby city lights?
Lillian Durante and John Zygowicz, Wauconda, Ill.

Dear Lillian and John,
Astronomer Dan Joyce of the Cernan Earth and Space Center at Triton College bemoans the advent of outdoor illumination and how it has muted what he calls "the grandeur of the night sky." For sky viewing, Joyce recommends Apple River Canyon State Park near Galena, the Green River Conservation Area west of DeKalb and Wildcat Mountain State Park west of Lake Delton, Wisc.
 
Joyce also suggests that you attend a general meeting (they're free) of one of the local astronomical societies and ask for advice. Besides Chicago Astronomical Society, there is Calumet A.S., Northwest Suburban Astronomers, Naperville Astronomical Association, and Skokie Valley A.S. to name a few.
 

We're anxious for some sun and warmth, especially after we've put a moderately harsh winter behind us, but it's not to be. Wednesday's sun was uplifting, but temperatures -- held down by northeast winds off Lake Michigan -- remained in the 60s across much of the city area. Southern sections, less affected by lake cooling, warmed into the 70s. Chicago's
official high of 67 degrees was nine degrees lower than usually chilly Anchorage, Alaska, which basked in 76-degree air. But things get worse today. Another storm system sweeps from the Great Plains across Illinois, and Chicago finds itself with clouds and rain, and even cooler temperatures.

Severe weather Wednesday afternoon

Severe thunderstorms rumbled across a huge area of the Great Plains Wednesday afternoon and evening. As of 9 p.m., the Storm Prediction Center had logged 12 tornadoes in seven states: Wyoming, Colorado, Nebraska, Kansas, Missouri, Oklahoma and Texas. A thunderstorm complex produced straight-line winds of 70-90 m.p.h. across large portions of the Dallas/Fort Worth area.

Dear Tom,
What is the coolest high temperature that has ever been recorded here in meteorological summer?
Nick Recchia, River Grove
Dear Nick,
One of the things than never ceases to surprise a student of Midwestern weather is its stubborn tendency to defy generalizations. The three-month period of meteorological summer began on June 1 and, by popular reckoning, summer is supposed to be the season of heat. It is, of course. In an average year Chicago logs 24 days (Midway Airport data) at or above 90 degrees, and 20 of them occur from June 1 through August 31.

But summer days also include a surprising number of cool days. On average, about one summer day in eight fails to reach 70 degrees; much less frequently, one in 78 remains below 60 degrees. Six summer days have even registered wintry chill -- highs only in the 40s. The coldest of them was June 5, 1895, with a high of 45.
 

What a difference a lake makes!  Lake Michigan's shoreline temperature at 60 is about 5 degrees cooler than this time last year.  The lake has had a profound impact on lakeside temperatures the past few days.  We have seen a spread of about 10 to 15 degrees from our cooler spots near the lake to our warmer spots west of the city.

  Monday's Highs:                        Tuesday's Highs:

Away from the lake                    Away from the lake

 83 St. Charles                            76 Algonquin

  Near the lake                            Near the lake

 72 Waukegan                             61 Wilmette

All those numbers come from combing the Weatherbug data archives.

There will be a wind off the lake through the end of the week so we will continue to see these wide ranges in high temperatures.   The combination of clouds and the wind of the lake will keep us about 10 degrees below average today.  Today's highs will feel more like the middle of May than the middle of June.

Tuesday's 67 degree high made it the coolest June 9 in 11 years, a reading more typical of early May and 11 degrees below normal.

Temperatures through the opening nine days of June are running 11.5 degrees below the same period a year ago, ranking June's opening among the 20 coolest here in 139 years of weather records. Myriad factors drive weather patterns, but it appears the persistence of wet weather through spring--it was the wettest spring on record at Midway Airport--on the heels of the wettest year on record in 2008 has produced a huge swath of wet soil across the Midwest. Wet soil inhibits warming by contributing to increased cloud cover and rain. Chicagoans have seen only 40 percent of the area's possible sunshine--well below the 68 percent considered normal.

Twisters and hail

Thunderstorms slammed sections of Kansas and Missouri producing seven twisters, more than 3 inches of rain and bombarding some locations with windshield-shattering hail. Sleeper, Mo., was hit with 2.75-inch diameter hail.

Dear Tom,
Is Phoenix's highest temperature still 122 degrees? If it is, did you know that so that date of the record 6/26/90 adds up to the temperature?
Mabel Shinouskis, Schaumburg
 
Dear Mabel,
We checked and the 122 degree high set on June 26, 1990 still stands as the all-time hottest reading in Phoenix so your numerology is still valid. That record came close to being challenged a few years ago when the mercury peaked at 121 degrees on July 28, 1995. Temperature records at Phoenix date back to 1896 and since then have varied from that 122 degree high to an all-time low of 16 degrees on January 7, 1913. So far this year (through June 9) the Arizona city has recorded 24 days of triple digit temperatures well on their way to annual average of 89. In 1989 Phoenix logged 143 days in the 100s, the most on record.
 

A tornado was reported by a trained spotter near Union Grove, just west of Racine, yesterday afternoon.  It was one of five tornadoes reported across the country on Monday.  Our Weatherbug network recorded a gust of 41 mph at Union Grove around 4 PM and a little over an inch of rain.  While we had some severe weather reports yesterday, overall this has been a quiet severe weather season so far.  There have been 716 tornadoes reported in the U.S. this year and that compares with 1088 through the same period last year.  There have been 21 deaths in 2009 from tornadoes and last year there were 126 deaths from tornadoes by the end of June.  There have been deaths reported in 7 states this year.  There have not been any deaths from tornadoes yet in Wisconsin, Illinois or Indiana.

Monday's thunderstorms hit in several waves. Downpours in pre-dawn storms totaled more than 2 inches (heaviest at DeKalb, 2.20 inches and Dixon 2.05 inches), prompting flood warnings in the west and northwest suburbs.

Afternoon storms hit hardest in northern counties and areas of southern Wisconsin. The strongest storms developed in southeast Wisconsin towering to heights of 45,000 feet. Ping-Pong-ball size hail struck near Mukwonago and high winds toppled trees. Several funnel clouds were sighted in the area. Blinding downpours also accompanied the Wisconsin storms, with nearly an inch of rain flooding streets in the Janesville area.

The storms formed on the heels of the area's most humid air mass since last September. Dew points, a measure of atmospheric moisture approached 70, readings typical along the Gulf coast.

Cooler weather will dominate the rest of the week, with another round of rain and thunderstorms on Wednesday. Warmer weather will return by the weekend, with highs returning to around 80 degrees.

Dear Tom,
What city in the world has the worst pollution? Not just air pollution, but all-around unhealthy conditions resulting from a degraded environment.
Richard Bemins

Dear Richard,
The Blacksmith Institute, a New York-based environmental group, recently released the results of an exhaustive survey of more than 300 of the world's most polluted places. The Blacksmith investigators, an international team of environmental and health experts that included faculty members from Johns Hopkins and Mt. Sinai Medical Center, carefully narrowed the list to ten cities. Here they are, grouped by primary pollutant: Lead contamination: Haina, Dominican Republic; La Oroya, Peru; Rudnaya Pristan, Russia; Kabwe, Zambia. Radioactive waste: Chernobyl, Russia; Mailuu-Suu, Kyrgyzstan. Coal dust: Linfen, China. Exotic chemicals: Ranipet, India; Dzerzinsk, Russia; Norilsk, Russia.
 

Thanks to John Franco for passing along this photo of a tree struck by lightning during some very "noisy" thunderstorms early Monday morning.

Photo by John Franco

Thanks to our long-time friend, pilot Anson Mount for sending us this shot taken this afternoon as the thunderstorms were passing east of the Waukegan airport.

Photo by Anson Mount

This thunderstorm prompted severe thunderstorm warnings in Kane County this afternoon
 
Mike Frankowski shares this photo with us of one of this afternoon's thunderstorm clusters in Kane County.  A severe thunderstorm warning was issued in response to it. Great photo--thanks Mike!
 
Tom Skilling
 


Photo courtesy of Mike Frankowski, South Elgin, Illinois

Thanks to Melissa McGuire for passing on this shot of a funnel cloud taken Sunday afternoon from a Denver suburb. The photo was taken by her brother Matthew Dupont who reported that everyone was OK and that it was "totally cool" to have some weather action here besides snow.

Photo by Matthew Dupont

The mercury could approach 80 degrees in Chicago Monday, a rare benchmark this season that has officially occurred only five times this spring. It will be humid as well, as southwest winds bring a surge of 60 degree plus Gulf-level dew points. The price for the warm, humid day will be showers and thunderstorms that could bring heavy rain, hail and high winds to portions of the metropolitan area.

The first batch of storms will arrive during the early morning hours of Monday with a potential for heavy rain. As these storms depart and skies clear, daytime heating could trigger another round of potentially severe thunderstorms in the afternoon. Cooler weather will follow as a cold front passes late Monday, setting the stage for another week of the northeast winds and cool weather that has been so dominant in recent months.

Record cold in the North Woods Sunday

A slew of record low maximum temperatures fell across the Upper Midwest Sunday. Antigo (48 degrees) and Merrill (49), both in northern Wisconsin, failed to top 50. Other record low highs included Green Bay (54), Oshkosh (56), Marshfield (50), Wausau (51) and Rhinelander (52). In Upper Michigan Marquette also established a record low high with a chilly 50.

Dear Tom,
I kept a diary during grade school and made an entry for July 4, 1956: "very cold, it snowed in Chicago a little." I don't think that officially occurred but could a flake or two have been reported?
Margaret Patterson
Dear Margaret,
It was a very cool 4th of July in 1956, but I can assure you that it did not snow. Chicago area temperatures did not climb out of the 60s that day, one that was marked by overcast skies, light rain and brisk east winds that gusted to 20 m.p.h. We had Chicago climatologist Frank Wachowski check to see if any hail occurred, but there were no thunderstorms in the area. In nearly 140 years of Chicago weather records the period from June 3 through Sept. 24 has remained completely snow free. July 1956 did start out on a very hot note with a record high of 103 degrees on the 1st before the cool weather moved in for July 4.

As June enters its second week, Chicago continues to experience cool
weather. Few area residents have even considered turning on the air
conditioning so far this season and some still have had their furnaces
running on recent cool mornings. Heat and humidity have remained bottled
up across the Southern states while a preponderance of north and
northeast winds have kept the city quite chilly. Except for a brief
intrusion of warmth and humidity Monday, little change in the cool
pattern is expected in the week ahead.

Showers and thunderstorms are expected to traverse the area today and
Monday. With temperatures in the 80s just south of Chicago colliding
with chilly 40s and 50s to the north, strong storms are possible with
the potential for some heavy rainfall through Monday evening. So far this spring there has been little severe weather in the Chicago area. While frequent rains have targeted the area, the lack of true warmth and 70 degree Gulf-level dew points have kept severe weather espisodes to a minimum.   

Record late-season snow hits North Dakota
The latest-in-the season measurable snow on record whitened portions of western North Dakota Saturday as two to three inches of snow fell near Dickinson. Several record lows were set across the upper Midwest Saturday including 27 at International Falls, 31 at Rhinelander, Wis., and 32 at Marquette,
Mich.

Dear Tom,
We are ending the first week in June and the city has not officially recorded an 85 degree high yet. When was the last time weather that warm was so delayed?
Barb Maple
Dear Barb,
In a typical year Chicago first officially reaches the 85 degree benchmark around May 15, but so far this season the warmest O'Hare Airport has been able to muster has been a high of 84 on three occasions: April 24 and again on May 20 and 21. It's been a dozen years since we've gone so late int