ASK TOM WHY: January 2009 Archives

Dear Tom,
We are getting a lot of snow this winter, but my grandmother says she remembers a
winter when there was very little snow, less than a foot. Is she correct?
-Ray Cosenbalun, Homer Glen

Dear Ray,
Your grandmother is almost certainly remembering Chicago’s back-to-back nearly
snowless winters of 1920-21 and 1921-22. The winter of 1920-21 was the city’s
least snowy, logging a scant 9.8 inches. The season’s biggest snow was a 2.1-inch
event on Jan. 3031, but despite the meager snowfall, Chicago did manage to eke
out a white Christmas, with one inch on the ground Christmas morning. The
following winter was nearly as snowstarved with only 11.5 inches falling. The two
winters combined produced 21.3 inches of snow—nearly 2 inches less than the
23.0 inches that fell during therecord Jan. 26-27, 1967, storm.

Dear Tom,
What has been Chicago's greatest snow depth at any one time?
Adam Zlotnicki, 9 years old
Dear Adam,
Many people think that Chicago's deepest snow cover occurred in the wake of
the city's 23-inch "Big Snow" of Jan. 26-27, 1967. Additional snowfalls
after the huge storm caused the city's snow cover to increase, reaching 28
inches on both Feb. 6 and 7, establishing an all-time record depth at that
time. However, that record was eclipsed during the city's benchmark winter
of 1978-79 that recorded 89.7 inches of snow. Chicago's snowpack reached 29
inches on Jan. 14, 1979, after 21 inches of snow fell from Jan. 11-14 during
the infamous "Blizzard of '79". That winter also holds the record for
consecutive days of snow cover: 100 days from Nov. 26-March 5.

Dear Tom,
With all the cold weather lately I know that it can get warm in January. What is the
nation's highest January reading?
Spencer G.

Dear Spencer,
It has never reached the 100 mark in the U.S. in January, but it has come close. The
nation's two highest January readings were both logged in 1997. The hottest was a
98-degree high at Indio, Calif., in the southern California desert near Palm Springs, and
the runner-up was a 97-degree maximum at Zapata, Texas near the Mexican border
between Brownsville and Laredo.

Closer to home, Illinois' peak January reading was a balmy 78-degree high recorded at
downstate Cahokia in 1986. Chicago has never reached the 70 degree mark in January
but the mercury did climb to 67 degrees on Jan. 25, 1950 and the "infamous" 65 degree
high on Jan. 24, 1967 two days before the 23 inch "Big Snow" on Jan. 26-27.

Dear Tom,
Everyone talks about the Jan. 26-27, 1967 23 inch "Big Snow." Didn't we have some
decent-sized snowfall in the weeks that followed?
Michael Balun, Plainfield

Dear Michael,
Indeed we did. The city was still reeling from the "Big Snow" when another 2.9 inches
fell on Jan. 29. That snow was followed by a 4.0 inch storm on Feb. 1 and a 7.6 inch
event on Feb. 5- that brought the city's snow depth to a staggering 28 inches.

Just 17 days later the city was walloped by a brief, but blinding blizzard that completely
snarled the evening rush hour. Accompanied by thunder and lightning, the storm
dropped visibilities to near zero across the area as winds gusting to nearly 50 m.p.h.
produced whiteout conditions. The storm brought 5.5 inches of snow to the city with
four inches falling in just 2.5 hours.

Dear Tom,
Our family planned a big party here in Chicago involving friends driving in
from out-of-town on a Sunday in January 1982. We postponed it to the next
Sunday because of incredibly cold temperatures, but that following Sunday
was just as bad, and we gave it up until the spring. What are the weather
details?
Jim Metzger
Dear Jim,
You had the great misfortune of planning your party on two of the absolutely
worst days in Chicago weather history. High/low temperatures on Sunday, Jan.
10, 1982, were 4 below zero and 26 below along with 30 m.p.h. winds and an
inch of snow that brought a virtual blizzard and treacherous highway
conditions. That minus 26 is Chicago's second-lowest temperature on record.
The following Sunday, the 17th, was nearly as bad. High/low readings of 4
degrees above zero and minus 23, plus two inches of windy snow made highways
treacherous again.

Dear Tom,
We've had a lot of days with snow cover this winter. What is the city's record for the
most consecutive day of snow cover? Have we ever had a totally snow covered March?
-Richard Lurie Chicago

Dear Richard,
Chicago's snowiest winter, the winter of 1978-79 with a record 89.7 inches of snow
also takes the honors for most consecutive days of snow cover. That winter the city
measured at least one inch of snow on the ground for 100 straight days from Nov.
26 through March 5. The season's snow cover peaked at a record depth of
29 inches on Jan. 14, 1979 in the wake of a 21 inch Jan. 11-14 snowfall. As for
March snow cover, the month has opened and closed snow-covered, but has never
sustained a snow cover for the entire 31 days. The city's longest duration March snow
cover was in 1960 when the ground was white from March 1 to 22.

Dear Tom,
We saw at least eight robins in our front yard this afternoon (Jan. 21)!
Does this mean we will be having an early spring?
The Burns Family, Westchester
Dear Burns Family,
Robins wintering in the Chicago area prompt questions like yours
occasionally, but the answer is a definite "no." Those robins aren't
foretelling an early spring, nor are they lost or confused.
In the summer, robins can be found across most of North America, even Alaska
and far northern Canada. However, those northern robins migrate south for
the winter, or west to the mild Canadian Pacific Coastal strip.
Surprisingly, most of the United States, including the Midwest, is wintering
territory for Canadian robins.
Locally, most (but not all) of our summer robins migrate to Southern states
for the winter, but some will remain here if they are able to find berries,
seeds and dormant insects.

Dear Tom,
Is there a specific name for the big chunk of frozen slush that accumulates behind the tire
of a car? During extreme cold weather those things are like rocks!
-Jeff and Linda Hildreth, DeKalb
Dear Jeff and Linda,
We know exactly what you're referring to, but to our knowledge, those ugly "fender
clinkers" are unnamed. Sometimes, though, it's worthwhile to take a look at the lighter
side of winter life (because a smile might make a winter like the current one a bit easier to
get through). With that in mind, we asked around. Here are two answers from Rick Burdsall
of Palatine: "Yes, but it's not printable in a family newspaper, especially after you've
stubbed your toe while trying to kick it loose. And, transportational aggregate— it's
composed of ice, salt and the material that used to be in all those potholes that have
formed on Interstate [Highway] 90."

Dear Tom,
Our mother told us that both my sister and I were born in snowstorms. She
was born on March 6, 1931, and I was born on Dec. 9, 1932? Can you provide
the details?
June Rohn, Elmhurst
Dear June,
It's true. Major snowfall followed both of your births, but your sister's
snowstorm was a much bigger event. From March 7-9, 1931, the city was hit by
16.4 inches of snow, the bulk of it (10.9 inches) falling on March 7. Your
snowstorm totaled only 6.5 inches, accumulating from Dec. 9-11, 1932. During
the early 1930s the nation was entering the "Dust Bowl" years, a period of
hot summers, extended summer drought and subpar winter snowfall. The
16.4-inch snowfall following your sister's birth accounted for 60 percent of
the entire 1930-31 winter total of 27.2 inches, and the December 1932 storm
provided nearly one quarter of the 28.1 inches that fell during Chicago's
winter of 1932-33.

Dear Tom,
After our recent subzero spell it was raining in Lindenhurst with a
temperature of 12 degrees. How can this be?
Bob Old, Lindenhurst Ill.
Dear Bob,
We get this question a lot in winter, but the answer bears repeating.

The form in which precipitation reaches the ground is not determined by the
surface temperature, but by the temperature profile from the ground to
cloud-level.

Most winter precipitation begins as snow, but if it encounters
a deep enough layer of above-freezing air as it falls to earth, the snow
melts and turns to rain. If the rain refreezes when it makes contact with
the below-freezing ground, the result is a glaze-producing freezing rain.

Freezing rain usually occurs at least a couple of times each winter in the Chicago area
but surface temperatures are usually in the 20s or very low 30s.

Dear Tom,
I live a few miles west of O'Hare Airport, and I recorded 20 degrees below zero on Jan.
16, when O'Hare went to 18 below. How many times has it been 20 below or colder in
Chicago?
Dan Klein
Dear Dan,
Twenty degrees below zero or lower is a rare occurrence in Chicago. In 138
years of official temperature records, (1871-2008 -- a period comprised of 50,404
days), 20 below or lower has been recorded on only 15 days. That's one day out of
3,360, or about once every nine years. However, their occurrences were not evenly
distributed. Five of the "minus 20 days" occurred from 1872-1899, and then 83 years
passed before the next one, 26 below in 1982. That initiated a "Little Ice Age" here,
because another eight of those frigid days came in rapid succession through 1985. The
last and most recent was 21 below, on Jan. 18, 1994.

Dear Tom,
My mother told me that it was in the 60s just before the 1967 "Big Snow"
started. Is she right?
Roger Hitchcock
Dear Roger,
Your mother is correct. Chicago's biggest snowstorm occurred 42 years ago on
Jan. 26-27, 1967. The mercury soared to a balmy record-breaking 65 degrees
on Jan. 24, a day when strong thunderstorms raked the city. Wind gusts to
nearly 50 m.p.h. knocked down a wall of a building under construction. The
temperature did reach 54 degrees on Jan. 25, but then cold air swept in and
the historic snowstorm began during the early morning hours of Jan. 26.
Snowfall totaled 16.4 inches on the 26th and another 6.6 inches fell on the
27th bringing the storm total to 23.0 inches, the city's all-time record
snowfall. Strong northeast winds gusting in excess of 50 m.p.h. piled the
snow into huge drifts, shutting the city down for days.

Dear Tom,
I read that Ronald Reagan's inauguration in 1985 was the coldest on record.
Wasn't that also the date of Chicago's all-time low of 27 below zero?
Lucy Pennington
Dear Lucy,
Sunday Jan. 20, 1985, is the date of Chicago's lowest temperature. Shortly
after 6 a.m. the mercury fell to minus 27, and combined with strong, gusty
west winds, windchills registered a numbing 77 below zero. The
inauguration is on Jan. 20, but because it was a Sunday, Reagan's
second-term inauguration public ceremonies were actually held the following
day--Jan. 21. The same arctic air mass that brought Chicago its
record cold had also invaded Washington, D.C. canceling the parade and
forcing most of the ceremonies indoors. At the time of the noon swearing-in
ceremony, the temperature was at 7 degrees, only a slight recovery from the
morning's low of minus 4.

Dear Mr. Skilling,
How fast do clouds go?
Stephanie Hanson, age 11
Dear Stephanie,
Clouds move at the same speed (and in the same direction) as the wind that
is blowing where they are located. Wind speeds increase as you go upward,
and that means the clouds that you watch in the sky are moving faster than
the winds blowing on your face. It also means the highest clouds move the
fastest.
Wind speeds of 10 to 20 m.p.h. are common at the ground, and winds on a very
windy day in Chicago rarely blow faster than about 35 m.p.h. But higher up,
wind speeds (and the speeds of clouds) are much greater. Winds of 30 to 40
m.p.h. are common at a height of 5,000 feet above the ground. The strongest
winds (and the fastest speeds that clouds ever move) are in the cores of the
most powerful jet streams about 6 to 10 miles aloft. Those wind speeds
sometimes hit 200 m.p.h.

Dear Tom,
With all the cold weather, a few co-workers and I were wondering: What were the hottest
and coldest months ever recorded in Chicago? Melanie in accounting suggested July 1955
as the hottest, and Maggie in payroll suggested January 1985 as the coldest. They
remember things like that.
Kenneth Palmer, Chicago
Dear Kenneth,
Melanie is on the mark, and Maggie is a little bit off. In 138 years of official weather
records, July1955 stands as the hottest month ever recorded in Chicago weather history.
The average temperature that month was a sizzling 81.3 degrees, and 19 days registered a
temperature of 90 degrees or higher. Chicago’s coldest month was January1977, with an
average temperature of 10.1 degrees. A reading of zeroor lower was logged on 17 days
that month. January 1985 ranks as 9th coldest with 14.4 degrees.

Dear Tom,
You refer to cold outbreaks from the north as the "Arctic Express" or the
"Siberian Express." Any difference?
Arthur Hitt, Richland Center, Wis.
Dear Arthur,
"Arctic Express" and "Siberian Express," while pleasingly descriptive, are
colloquial, non-technical terms whose definitions have never been formally
or precisely stated -- and add "Pineapple Express" to the list, because it
often occurs simultaneously with the other two.
Those terms describe patterns of upper "steering winds" (generally 15,000 to
30,000 feet aloft) that direct surface air masses from the tropical Pacific
Ocean to Alaska (Pineapple Express), from the Alaskan/Canadian Arctic deep
into the Lower 48 (Arctic Express) or from eastern Siberia and the
Alaskan/Canadian Arctic similarly deep into the Lower 48 (Siberian Express).
"Siberian" implies an air-mass origin northward from Alaska and Canada.

Dear Tom,
How many days in the winter does the temperature here in Chicago drop to zero
degrees or lower?
Jeff Honeycutt, Chicago
Dear Jeff,

It's greatly dependent upon where you are located in the metropolitan area. All the heat
generated in a city eventually escapes into the air, and Chicago promptly removes
snow, which effectively radiates heat away. In addition, Chicago sits adjacent to Lake
Michigan, whose water is a potent winter heat source. Chicago is therefore an "urban
heat island" whose effect, greatest in the core of the city near the lake, diminishes
outward into the suburbs and the rural countryside.

On average, the Loop experiences about six days annually with nighttime low
temperatures at or below zero; inland about four to seven miles, that number increases
to eight or nine days, and at ten miles, to 11-12 days; still farther out, in the rural
countryside, especially to the west, to 15 days.

Dear Tom,
What is the date that Chicago's average temperatures start rising?
Joe Hoffman
Dear Joe,
We are rapidly approaching the mid January period that Chicago's average temperature
reaches its lowest value of the year--21 degrees, specifically from Jan. 13-18, after
which it begins it slow, but steady climb to the year's peak of 74 degrees from July
15-31.
These temperatures are derived from the current set of climatological normals
based on temperatures from the 30 year period from 1971-2000. The annual
temperature climb starts slowly gaining only two degrees to 23 by the end of January
but then gathers steam, reaching 31 by the end of February and 43 by the end of March.
Average readings climb to 53 by April 30, 64 by May 31 and to 72 by the last day of
June before leveling off after reaching the mid-to late-July peak.

Dear Tom,
What is greatest 24-hour snowfall ever recorded in Illinois? How about the state's record low temperature?
Thanks, Ed Berling Lockport, Ill.

Dear Ed,
It may come as somewhat of a surprise that both of these records were set in central Illinois and not in the normally colder and snowier far northern portions of the state. Illinois' greatest 24-hour snowfall dates back to a huge snowstorm that raked the central Midwest back on February 27-28, 1900 bringing 37.8 inches of snow to Astoria located southwest of Peoria. The storm center moved northeast out of Texas across southern Kentucky on a track that took it to northern Virginia. The all-time low temperature for the state was set just 10 years ago during a major arctic outbreak on the morning of January 5, 1999 when the mercury plunged to 36 degrees below zero at Congerville just east of Peoria.

Dear Mr. Skilling,
Exactly what is a blizzard?
James Osborne
Dear James,
It's a misunderstood word, and it is often erroneously applied to storms that bring very
heavy snow. The National Weather Service defines a blizzard as a severe winter storm
with sustained winds or frequent wind gusts of 35 m.p.h. or higher and visibility
reduced by falling or blowing snow to 1/4 mile or less for at least three hours. The
National Weather Service will issue a blizzard warning when a winter storm is expected
to meet the wind and visibility criteria. Note that snow accumulation is not a criterion,
and a blizzard can actually occur with clear skies if the visibility reduction is caused by
blowing snow.

Because buildings block and slow winds, weather conditions in winter storms are
usually less harsh in cities. Urban dwellers often greatly underestimate the severity of
blizzards in open, rural areas.

Dear Tom,
In the winter of 1978-79 I remember a very snowy December and then came that
snowstorm that shut the city down. Was it on Jan. 1?
Mark, Fox Lake, Ill.
Dear Mark,
The winter of 1978-79 was Chicago's worst. It boasts an all-time record 89.7
inches of snow, plus a record 100 consecutive days of snow cover from Nov.
26 to March 5. December was very snowy with 31.4 inches accumulating,
including a New Year's Eve blast that brought 7.6 inches. But that snowstorm
was the famed "Blizzard of 79" that dumped 21.0 inches of snow on Chicago
from Jan. 11-14, bringing the city to a standstill. Snow was piled so high
that people tied flags to their cars so they could be seen as they
approached snow-clogged intersections. Side streets were impassible, and
many cars could not be moved until the snow finally melted.

Dear Tom,
In the 1946 movie "Gilda," Rita Hayworth sang "Put the Blame on Mame," a song that
mentions the Great Chicago Fire and the Blizzard of 1886. What’s the story with
the blizzard?
--Heikki Heino, Crete

Dear Heikki,
The blizzard of 1886 that the song references took place in Manhattan, not Chicago. The
storm began in New York the evening of Jan. 8, 1886, and when it ended, as much as 12
inches of snow covered Manhattan. The storm was accompanied by very high winds, and
drifting was severe. It took days to remove the snow, and newspaper accounts refer to
banks of snow up to 6 feet high lining the streets "as far as the eye could see." Before
reaching NewYork, the storm brought heavy snow followed by bitterly cold air to much of
the Midwest. Chicago didn't get much snow, but temperatures here plunged to 9 degrees
below zero in the storm's wake.

Dear Tom,
What are the highest and lowest barometric readings ever recorded in the
Chicago area?
Jack Wiaz, Highland Park
Dear Jack,
The National Weather Service and its precursor agencies have been recording
barometric pressure in Chicago since late 1870. During that period, an
endless parade of highs and lows have resulted in a barometric span of 2.28
inches of mercury between the city's pressure extremes. On March 12, 1923,
an intense storm system passed close to the city, bringing rain and
thunderstorms along with the city's lowest-ever barometer reading of 28.70
inches. On the up side, the highest barometer reading was recorded nearly 20
years ago on Feb. 16, 1989, when an arctic high settled over the upper
Midwest, sending the mercury here to a lofty 30.98 inches. Despite the very
high pressure, it was not exceptionally cold that day with a high of 26 and
a low of 8.

Dear Tom,
A recent column set the record straight that Chicago never had a month-long below
zero streak. However, didn't we have a string of below freezing days that lasted more
than a month?
Mel Theobald Chicago

Dear Mel,
We sure did. In the winter of 1976-77, Chicagoans endured a frigid 43 day stretch
where the mercury never broke the freezing mark. The temperature fell to 32 degrees at
1 p.m. on Dec. 27, 1976 and did not reach the 32 degree mark again until 10 a.m. Feb.
9, 1977. During this unprecedented subfreezing spell, the city logged 22 days with low
temperatures of zero or below. The coldest day was Jan. 16 with a high of only 7 below
and a low of minus 19. Snow fell on 29 of the 43 days with more than a foot from Jan.
8-10. Once the streak ended, mild weather returned with the city recording a balmy 52
by Feb. 11.

Dear Tom,
A recent column referred to the "old windchill formula". When and how was it
changed?
Marie Stevens
Dear Marie,
From 1973 through early 2001 the National Weather Service computed windchill based
on a formula developed in the 1940s by Antarctic explorers Paul Siple and Charles
Passel. Windchill values became iconic in Chicago during the brutal winters of the late
1970s and early 1980s when they frequently dipped as low as 50 to 80 degrees below
zero. However, later research concluded that these derived windchill values were too
low, and in Fall 2001 a new formula thought to be more realistic in the assessment of
the effect of wind and cold on human flesh, was implemented. Using the new formula a
temperature of 10 below with a 20 m.p.h. winds would produce a minus 35 windchill
compared to 53 below zero with the old formula.

Dear Tom,
In what ways are the jobs of a meteorologist and a climatologist similar?
Dr. Leon Hoffman Chicago

Dear Dr. Hoffman,
Both professions are involved with the study of weather and the atmosphere,
but in general a climatologist deals with categorizing, cataloging and
ranking weather that has already occurred while a forecaster's challenge is
to predict the weather conditions that lie ahead. Climatologists provide a
wealth of information that helps meteorologists formulate their forecasts by
putting them in historical perspective through documentation of past weather
events and extreme conditions. A forecaster may be considering the issuance
of a forecast calling for an unusual event and proceed with added caution
when climatological analysis reveals that the expected weather would be a
very rare or unprecedented happening.

Dear Tom,
One of my coworkers claims that during early 1980s Chicago temperatures did
not rise above zero for an entire month. I can't remember any period that
cold. Can you clear this up?
Barry Rosenberg
Dear Barry,
Chicago did experience an historic cold spell in 1983, but nowhere near the
magnitude described by your co-worker. The period in question occurred around
Christmas 1983. Temperatures in Chicago dropped below zero at 7 a.m.
Dec. 22 and did not break the zero mark again until 11 a.m. on Dec. 26
--a record 100 consecutive hours at or below zero. During this period the city
not only recorded its coldest Christmas Eve, with a low of minus 25, but also
its all-time coldest Christmas with a high of 5 below and a low of 17 below.
December 1983 was an extremely cold month averaging only 14.3 degrees- a
stunning 13.4 degrees below normal.

Dear Tom,
Are there any portions of the country that are still considered to be in a
drought?
Patrick Carry, Waukegan
Dear Patrick,
Portions of the United States are still experiencing drought conditions but,
broadly speaking, drought is in retreat nationally. Winter is the most
favorable time of year to overcome drought across most of the United States
because temperatures are lower, and evaporation rates, compared to other
seasons, are minimal. Then too, actively growing plants draw huge amounts of
water from the soil, but vegetation, except for milder portions of the
southern United States, is dormant during the winter. On balance, a far
greater proportion of winter precipitation recharges soil moisture than in
other seasons. Pockets of severe but diminishing drought exist across the
western third of the nation, and the Southeast is pulling out of a two-year
drought. Texas, too, is still very dry.

Dear Mr. Skilling,
What is WMO?
Larry Fhaner,9
Dear Larry,
Those letters stand for the World Meteorological Organization, the United Nations agency
that deals with weather and climate. The WMO is headquartered in Geneva, Switzerland..
The WMO describes itself as "The UN system's authoritative voice on the state and
behavior of the Earth's atmosphere, its interaction with the oceans, the climate it
produces and the resulting distribution of water resources." Because the atmosphere
knows no national boundaries, the WMO believes the issues of weather and climate are
best served by an unrestricted exchange of weather information, and it encourages
international cooperation in that regard. That’s quite a mouthful, and I recommend you
visit the WMO's Web site: www.wmo.int/pages/index_en.html

Dear Tom,
The moon revolves around the Earth, and other planets in the solar system
have a few moons. Do any of those moons have their own moons?
Robert Miller, Chicago
Dear Robert,
You might be surprised to learn that the population of moons in our solar
system is considerably larger than "a few." The Earth has one, but at least
60 moons are in orbit around Jupiter, and Saturn boasts a minimum of 52.
We suggested to astronomer Dan Joyce of the Cernan Earth and Space Center
at Triton College that it would seem theoretically possible for moons to
have moons, but conflicting gravitational fields might pull them out of
orbit.
Joyce responded, "Yes, it's theoretically possible for moons to have moons,
but no, there are none known. By the way, our own moon does have artificial
satellites that are not in any danger of being yanked out of orbit any time
soon."

Dear Tom,
It's been rather snowy so far this winter. However, when was the last time
we recorded 10 or more inches of snow from a single storm in Chicago?
Dan Metcalf, Lisle
Dear Dan,
Residents of northeast Illinois know from brute experience it's not just
the amount of snow that determines a storm's impact, but a variety of
intertwined factors -- rate of snowfall, temperatures, winds, the time of
day, the day of the week, and the accuracy and timeliness of weather
forecasts leading up to the event -- to name a few. But big storms can
temporarily overwhelm any city, and a "ten-incher" is a big storm. Chicago
has logged 40 snowstorms of 10 inches or more in 124 years, or an average
of one every three years. The most recent storm of that magnitude was 10.2
inches on Feb. 12-13, 2007. Remember, though, that snow totals in any given
storm vary greatly across the city area.