Dear Tom,
With November beginning, I'm wondering what the month's weather extremes are in Chicago.
--Tarleton Edwards Dear Tarleton,
Dear Tarleton,
November weather in Chicago transitions from autumn to winter, sometimes gradually but often harshly and abruptly. Normal high temperatures decline more rapidly than in any other month --on average 1 degree every other day (from 55 degrees to 40). At its extremes, November weather displays a split personality. The month's highest temperature, 81 degrees (recorded on Nov. 1, 1950), and its lowest temperature, 2 degrees below zero (Nov. 24, 1950), occurred only 23 days apart. November usually brings the season's first accumulating snow, and the average monthly snowfall is 2.2 inches --- but 14.8 inches came down in November 1940.
Dear Tom,
The first day of winter is Dec. 21, the shortest day of the year. Days start lengthening after that and the Earth also gets closer to the sun. So why does Chicago continue to get colder almost to February?
Bob Thurston
Dear Bob,
The sun is 2.8 million miles closer to Earth in early January than it is at its most distant point in early July. However, the effect of that "closeness" is overwhelmed by the effect of the tilt of our planet's axis relative to the sun. That tilt situates the Northern Hemisphere away from the sun's most direct rays, thereby reducing the amount of solar energy available for heating.
Other cooling factors such as round-the-clock darkness and widespread snow cover in the polar north prove far more important in determining temperature than closeness to the sun, and cold air continues to expand its dominance well into January.
Dear Tom,
I moved to Chicago several months ago and I've heard that winters here are brutal. Does the cool weather now mean this winter will be even more brutal than usual?
Tami
Dear Tami,
Take heart. A review of Chicago's autumn and winter temperature statistics in years past shows that a chilly October (such as we're experiencing this year) is usually followed by an abrupt temperature turnaround. Winter is cold, of course -- Chicago's winters are always cold -- but a winter with above-normal temperatures often follows an October with subnormal temperatures.
May we take exception to your characterization of Chicago winters as "brutal"? We believe that's too harsh. If you moved here from a milder climate, as your question implies, Chicago's winter weather will shock you initially, but you'll quickly become acclimated.
Dear Tom,
We're planning an ocean-side vacation at Waikiki Beach in Honolulu, Hawaii, and have become concerned about the tsunami threat. Any thoughts?
Kim Larson
Dear Kim,
The catastrophic tsunami of Dec. 26, 2004, in the basin of the Indian Ocean raised worldwide awareness of the deadly potential of such occurrences. Your concern is justified because, despite the Indian Ocean event, the Pacific Ocean, in which Hawaii is located, is encircled by the notorious "Ring of Fire" and is the world's most tsunami-prone ocean.
That said, be advised that Hawaii has had long experience with tsunamis and, with the National Weather Service's "TsunamiReady Program," has an excellent warning system in place. The Weather Service's Pacific Tsunami Warning Center, located in Ewa Beach, Hawaii, with a staff of 15, maintains 24-hour vigilance.
Dear Tom,
Our 5th grade science class is studying the sun. Can you tell us the highest and lowest temperatures in the world?
Chloe, Justin, Michael and Danielle
Fernway Park School, Orland Park
Dear students,
The temperature extremes on our planet span an amazing 265 degrees. The world's highest temperature of 136 degrees was recorded at El Azizia, Libya, on Sept. 13, 1922. Contrast that to a low temperature of minus 129 degrees measured at Vostok, Antarctica, on July 21, 1983. Temperature extremes in the U.S cover a substantial but smaller range of 214 degrees. The nation's highest temperature was 134 at the Greenland Ranch in Death Valley, Calif., on July 10, 1913. The lowest was 80 degrees below zero at Prospect Creek, Alaska, on Jan. 23, 1971. Excluding Alaska, the lowest reading in the Lower 48 was minus 70 at Rogers Pass, Mont., on Jan. 20, 1954.
Dear Tom,
While the Halloween 1991 "Perfect Storm" was raging in the Atlantic, Minneapolis was hit with a major snowstorm. Were the storms related?
--Rick Mullin
Dear Rick,
Though occurring half acontinent apart, the storms, though separate entities, were related. The "Perfect Storm" made famous by Sebastian Junger's novel and the movie raked the Eastern Seaboard from Oct. 30 to Nov. 1, 1991. At the same time an equally amazing storm was bringing record snowfall to Minnesota. From Oct. 31 to Nov. 2 the blinding snowstorm dropped 28.4 inches of snow on the Twin Cities, a single storm record. Duluth was buried by 36.9 inches, the largest storm total in Minnesota history. Because of the strength of the Atlantic storm, the Midwest storm could not move east and was forced north, prolonging the snow in Minnesota.
Dear Tom,
I received an email showing people walking on a frozen Niagara Falls in 1911. Is that real, and if so how cold was it?
George Koziol, Chicago
Dear George,
Those photos have been making the rounds for many years. While not commenting on their validity but only on the weather, they were probably not taken in 1911 but in late January or early February 1912 when severe cold gripped the Great Lakes region. Weather records indicate that January 1912 was the coldest January on record to date in the Lakes region, not only in terms of average temperature but in consecutive days of below zero weather. Buffalo recorded only five days with highs above freezing during all of January. Intense cold continued in early February, and that six-week period ranked as one of the coldest on record at that time. Buffalo did not climb above freezing from Jan. 30-Feb. 16 and dropped to 13 below zero on Feb. 10.
Dear Tom,
In your Oct. 22 column you mentioned that 1992 had the fewest number 80 degree or higher days (58) before this year (56). What was the winter of 1992-93 like?
Frank Davis Prospect Heights
Dear Frank,
The winter of 1992-93 was slightly above normal in both temperature and snowfall. The winter averaged 26.4 degrees---about a degree warmer than a typical Chicago winter. There were only four days of subzero weather, with the winter's lowest reading dropping to just minus 4 degrees on Feb. 24. Snowfall totaled 46.9 inches as compared to a city-wide average of about 40 inches. There were no huge snowstorms---the biggest totaling around 7 inches, and the season's deepest snowpack reached only 8 inches. The winter's first major snow, a 5 inch affair, did not occur until Dec. 9-10.
Dear Tom,
Is it true that Chicago had twice as many days of 80 degrees or higher in 2007 than we have had this year?
Pat Byrne Hoffman Estates
Dear Pat,
This year's lack of warm days has been extraordinary. So far in 2009 Chicago has logged only 56 days at Midway Airport where the mercury has reached at least 80 degrees. That is the lowest total there since records began in 1928, besting the previous record of 58 days during the cool summer of 1992 when volcanic haze from Philippine volcano Mt. Pinatubo reduced temperatures world-wide. Ironically the year with the most days of 80 or higher was one year earlier in 1991 with 108. In 2007 the city reached 80 or higher 103 times falling a little short of doubling this year's anemic number.
Dear Tom,
What does a cool October say about the following November? Here's hoping your crystal ball can offer some good news.
Doug Geist
Dear Doug,
Indeed it can. A review of Chicago's historical October and November temperature data indicates that far below-normal temperatures in the Oct. 1-19 period (such as we have experienced this year) do not carry into November. A sharp temperature turnaround usually occurs.
This year, October's temperatures (through the 19th) have averaged 46.9 degrees -- 8.0 degrees below normal -- and that is the chilliest Oct. 1-19 in the 51 years for which temperature data are available at O'Hare International Airport.
We looked at November temperatures following ten comparably chilly Oct.1-19 periods. The good news is that temperatures in nine of those ten Novembers were at or above normal.
Dear Tom,
Why are weather people called meteorologists? Since they deal with the weather and not meteors, it seems more appropriate to call them "weatherologists."
Claire Gerbeck, Oak Park
Dear Claire,
The derivations of many words in the English language can be traced to the languages and literature of ancient cultures, and such is the case with "meteorology." It dates back to early Greece, when anything that was suspended in the air or fell from the sky (clouds, rain, rainbows, meteorites, etc.) was referred to as a "meteor."
Aristotle (384-322 B.C.) presented a series of treatises on natural phenomena in 340 B.C. Entitled "Meteorologica," they covered that era's knowledge of weather, astronomy and related subjects. Because much of "Meteorologica" dealt with weather, the term meteorology became linked with weather and atmospheric studies.
Dear Tom,
Growing up in Chicago in the 1950s I remember an October with some very heavy rain and a lot of flooding. What year did that occur?
--Stuart Chambers
Dear Stuart,
Without a doubt you are remembering October 1954, the city's wettest October on record. The month recorded an official 12.06 inches of rain with most of it falling early in the month. During the morning of Oct. 3, thunderstorms dumped nearly 4 inches of rain that produced widespread flooding of basements and viaducts. Less than a week later devastating floods returned as Midway Airport recorded 6.72 inches of rain in a span of 48 hours between Oct. 9-11. West and south portions of the metropolitan area got 10 to 12 inches. A number of Loop buildings were flooded, and the Chicago River rose so high that numerous bridges were inoperable.
Dear Tom,
Do you happen to know the derivation of "blizzard"?
Robert Gow
Dear Robert,
It's a relatively recent word, and it originated in the United States or England. By the early 1800s in this country, blizzard meant a cannon shot, a rapid volley of musket fire or a severe blow. Frontiersman Davey Crockett (1786-1836) was described as "speaking a blizzard" (a verbal blast) during a dinner speech and, on another occasion, taking a blizzard (a volley of shots) at a deer.
At about the same time in the English Midlands, blizzer referred to a severe wind and snow storm.
The first documented published uses of blizzard appeared in a few newspapers in Iowa in March and April of 1870 to describe a fierce winter storm in that area. Thereafter, blizzard came to be recognized as descriptive of a severe, wind-driven snowstorm.
Dear Tom,
A couple days ago, while talking about a powerful storm hitting California, you mentioned heavy snow in the mountains, but here in Tahoe, at 6,200 feet, it was pouring rain.
Jimmy Smith, Tahoe, Calif.
Dear Jimmy.
Early-season snowstorms in California's mountains are usually confined to the most lofty elevations of the Sierra Nevada Mountains. It's a matter of atmospheric physics. Air expands and cools when it rises, losing 5.4 degrees for every thousand feet of vertical ascent in clear air and 3.3 degrees when it is saturated with moisture (in fog or clouds). When humid air from the Pacific Ocean ascends the Sierra Nevadas, it cools at a rate of 5.4 degrees per 1,000 feet of vertical rise until clouds form, after which the chill rate occurs at 3.3 degrees per 1,000 feet. Rain at Tahoe (6,200 feet) at, say 40 degrees, would likely be snow at 30 degrees at 9,200 feet.
Dear Tom,
So far this October the highest temperature has been just 62 degrees and the forecast calls for continued chilly weather. Have we ever had an October that has failed to produce a 70 degree day?
Gene Maxwell
Dear Gene,
October is usually Chicago's last nice month before the dark, damp and chilly days of winter set in. Typically the area sees about 10 days with highs of at least 70 degrees, and usually there are at least a couple of days in the 80s. Checking temperature records dating back to 1870, climatologist Frank Wachowski found only two Octobers that failed to produce 70 degrees--1885 and 1917. In sharp contrast to those years, October 1963, the city's warmest on record, was a banner year for days of 70 or higher-- with 24 on the books. That month tallied 11 days in the 70s, 12 in the 80s and even a 94 on Oct. 6.
Dear Tom,
We will be vacationing in Hawaii the entire month of February. What might be the effects of El Nino there?
Lucille Pirri, Deerfield
Dear Lucille,
El Nino, abnormal warming of water in the eastern tropical Pacific Ocean, is now occurring and is forecast to persist at least several months. The weather impacts of El Nino are global in scope, something Chicagoans, situated in the central United States, easily overlook.
The weather effects of El Nino are greatest in winter, and in Hawaii the primary impact is drought. That's bad news because water is chronically in short supply in Hawaii, and the islands are already experiencing severe drought. El Nino is likely to exacerbate the situation.
Other effects: lighter trade winds than usual and booming surf on west- and north-facing coasts. Finally, hurricanes, rare in Hawaii, are somewhat more frequent in El Nino years.
Dear Tom,
Most of our weather moves from the west, but hurricanes in the Atlantic Ocean move to the west. Can you explain this?
Paul Knauth
Dear Paul,
Hurricanes move with the wind flow in the layer between the surface and approximately 40,000 feet aloft. During the summer and fall, a belt of more or less permanent high pressure extends across the Atlantic Ocean between the United States and northern Africa, paralleling the Equator.
Winds spiral out of the high in a clockwise direction and generate prevailing easterly flow across the tropical Atlantic, where most hurricanes form. Those prevailing easterlies steer hurricanes to the west, with a slight northward component. As hurricanes continue on that path, they eventually get caught in southwesterlies on the poleward side of the high pressure belt, and they "recurve" to the northeast.
Dear Tom,
I remember a wonderfully warm Halloween when we trick-or-treated until our legs wore out. I think it was 1955. Can you clarify?
Judy Campbell, Orland Park
Dear Judy,
Though the early 1950s featured several warm Halloweens, 1955 was definitely not one of them. That year Oct. 31 started out very chilly with temperatures in the 30s along with some snow flurries, and though it warmed up a bit in the afternoon, the high reached only 51. If your time frame was off a few years, you might be remembering the city's warmest Halloween on record which occurred in 1950 with a summery 84 degree high. Other possibilities include 1952 (69 degrees), 1953 (70) and 1956 (68). After a string of recent cool Halloweens, last year turned out quite nice with the high temperature topping out at a balmy 70 degrees.
Dear Tom,
What is the warmest surface temperature at which it can snow?
--Tim Guimond
Dear Tim,
Checking through weather records, we found a case where it snowed during the 1970s in Jacksonville, Fla., when the temperature was 53 degrees. Temperatures were quite cold just above the surface and the air was very dry, which allowed cooling from evaporation to prevent the flakes from melting. In order for snowflakes to form, cloud temperatures must be 32 degrees or lower and the flakes must be able to survive the fall to the ground without melting. According to Chicago climatologist Frank Wachowski, snow has fallen here with temperatures as high as the middle 40s, but the flakes melted upon contact with the ground. Chicago's latest-in-the- season trace of snow occurred on June 2, 1910, when it was 44 degrees.
Dear Tom,
"Something good comes of everything," is my dad's favorite saying. So, can you tell me what good might have come out of our cloudy, cool, rainy summer?
Joseph Heard, Chicago
Dear Joseph,
Many people dislike hot weather and enjoy rain and cloudiness; they were pleased. Here's something less obvious, but significant: less ozone air pollution.
According to the EPA, many U.S. cities from the Midwest to the Mid-Atlantic and Northeast experienced a summer with at least 80 percent fewer days on which ozone pollution reached unhealthy levels. Chemical reactions between nitrogen oxides and volatile organic compounds in the presence of sunlight produce ground-level ozone, conditions likely to occur on hot, stagnant summer days. This summer's cool temperatures and above average rainfall and cloudiness were unfavorable for ozone formation.
Dear Tom,
What should the weather be like in Rio de Janeiro for the 2016 Olympics?
R. J. McGee Chicago
Dear R.J.,
August is a very pleasant late winter month in Rio de Janeiro, which lies at the south end of the tropics just north of the Tropic of Capricorn. The 2016 Olympics will be held from Aug. 5 to 21, a time of year when daytime highs typically run in the middle 70s with morning lows in the middle 60s.
Temperature extremes for the month range from a high of 93 to a low of 54.
August is usually a dry time of the year in Rio with measurable rain falling on an average of just seven days during the month which typically receives 1.7 inches of rain. Humidity levels which can be oppressive during the Brazilian summer are moderate in August, and being a coastal city, Rio experiences frequent cooling breezes off the Atlantic.
Dear Tom,
A friend of mine from Ecuador told me that the weather Quito is almost always pleasant. Is this true?
Jeff Taylor Chicago
Dear Jeff,
Quito is located on the equator more than 9,000 feet above sea level and has a climate described as "eternal spring" with mild days and chilly nights. Temperatures are relatively steady through the year with daytime highs generally in the upper 60s and lower 70s and overnight lows in the 40s and 50s. The area's hottest days top out in the middle and upper 80s
and the coolest mornings drop to around freezing. The variable aspect of Quito's weather is mountain-induced rainfall with the city having definite wet and dry seasons. The dry season runs from June through September with monthly rainfall averaging 1 to 3 inches while the October to May rainy season has considerably more with amounts in the 3 to 7 inch range.
Dear Tom,
What is the earliest occurrence of measurable snow in Chicago?
Tanya Davis
Dear Tanya,
With the opening of October upon us it is time to start thinking about snow. Though the season's first measurable snow doesn't usually occur here until the middle of November, the city has experienced measurable snowfall on many occasions in October. The city's earliest measurable snowfall on record took place here just three years ago on Oct. 12, 2006 when both Midway and O'Hare airports measured 0.3 inches of snow. The snow was more significant in the northwestern suburbs where 1.2 inches fell at Mundelein and one inch at both Algonquin and Crystal Lake. One reason the snow was able to accumulate that morning despite the still warm ground was the intense rate of fall, that reduced visibilities to near zero in some areas.
Dear Tom,
Has there even been a tornado produced by a snowstorm or when snow was on the ground?
Mike Callan Lemont
Dear Mike,
It is common for tornadoes to develop on the warm side of storms that deliver heavy snow, but it would be extremely rare for a twister to develop on the cold, snowy portion. Recently, on Feb. 5, 2008, 64 twisters battered the South while heavy snow swept the central Midwest. Though twisters usually form in a warm, moist surface environment, there are always exceptions. Dr. Harold Brooks of the National Severe Storms Laboratory in Norman, Okla. tells of a twister at Altus, Okla., on Feb. 22, 1975, with temperatures near freezing. The F2 storm killed two and injured 12 as it ripped through a trailer park. Twisters have also occurred during warm-ups when pre-existing snowpacks have not melted.
Dear Tom,
Can you suggest a place where the normal summer weather is moderate, with pleasant humidity and only rare 90-degree days? And in addition, where the climate is temperate year around?
Steve Cepa, Libertyville
Dear Steve,
Let's preface the answer with this comment: Even locations that normally enjoy year-around temperate weather will at times experience periods of extreme temperature and humidity conditions.
That said, within the continental United States coastal central and southern California probably comes closest to satisfying your criteria, both during the summer and year around -- roughly the area from Monterey to San Diego. And by "coastal" we mean within a few miles of the Pacific Ocean. Hot days as defined by 90 degrees or higher rarely occur there (versus Chicago's average of 24 days at Midway Airport) and winter readings in the 20s or lower are also rare.
Dear Tom,
Do you think anything can be done about the increasing levels of carbon dioxide in the atmosphere?
--Jim Wilson
Dear Jim,
Increasing atmospheric concentrations of carbon dioxide (CO2), up from 316 parts per million in 1960 to 383 parts per million in 2008, is of concern because, as a greenhouse gas, it is implicated in the issue of global climate change, and human activity adds about 34.5 billion tons of CO2to the atmosphere each year. To date, efforts to deal with this situation have focused on reducing emissions, but it is unrealistic to suppose that significant reductions are likely to be accomplished. However, Columbia University professor Wallace Broecker and his associates have proposed a novel approach: economically removing CO2 from the atmosphere, and they are perfecting a prototype device to do just that.
Dear Tom,
I enjoyed your column in which you explained why cumulus clouds have flat bottoms. Is there some way that an amateur weather buff and avid cloud-watcher like me can estimate how high those flat-bottomed cumulus clouds might be?
Andrew Browning
Dear Andrew,
Cumulus clouds form when warm air in the surface layer (that is, air within a few hundred feet of the ground) rises sufficiently far upward to be chilled to saturation so that its load of water vapor begins to condense into visible cloud droplets. The height at which that occurs depends mainly
on the temperature and moisture content of air (as indicated by the dew point) in the surface layer.
The height (in feet) above ground of the base of cumulus clouds can be estimated quite accurately with this rule of thumb: Subtract the dew point from the temperature and multiply the result by 230.
Dear Tom,
Why is it that clouds are flat at the bottom and have irregular shapes on top?
Hans Weckerle
Dear Hans,
You have described cumulus clouds, the "dab of cotton" clouds that populate the sky on warm afternoons. When warm air ascends in rising currents, its pressure falls and its temperature drops at a steady rate of 5.4 degrees per 1,000 feet of vertical climb.
Rising air, if the process continues long enough, eventually ascends to a critical height and chills to a critical temperature at which its load of water vapor suddenly begins to condense. That defines the flat bottom of a cumulus cloud.
However, ongoing condensation at the cloud top, rather than being limited by specific air pressure and temperature values, occurs in irregular surges determined by constantly varying factors like available moisture and updraft strength.
