Dear Tom,
I was married on Dec. 8, 1945 and it was a very warm day. A week later when my friend got married on Dec. 15 it was below zero. Can you provide the details?
Delores Faltynek Antioch
Dear Delores,
We asked climatologist Frank Wachowski to check the weather archives and he found your recollections to be right on---illustrating how quickly Chicago weather can change this time of the year. You wedding day was indeed very mild with a balmy high of 53 degrees. Your friend was not as fortunate as winter hit with a vengeance in the following week. A cold front dropped temperatures into the 20s and a major snowstorm followed on Dec.13 and 14 bringing about 4 inches of snow. Your friend's Dec. 15 wedding took place on a very wintry day with a high of just 11, a low of 2 below zero and 4 inches of snow on the ground.
Dear Tom,
I am putting in a bid for sidewalk snow removal in the Lincoln-Belmont-Ashland shopping area. Can you provide the average frequency of the number of snows per season of various amounts?
Bill Haderlein, Chicagoland Deck Cleaning & Sealing
Dear Bill,
Indeed we can. The following statistics are derived from 80 years (1929-2008) of Midway Airport snowfall data, courtesy of Chicago weather historian Frank Wachowski.
On average, Chicago receives at least one-half inch of snow 17 times per snow season. Snow storms in the range of 1-3 inches occur about 7 times; 4-6 inches, twice; 7-10 inches, once; more than 10 inches, about once every other year.
A note of caution: The number of storms that might occur in any given snow season varies greatly from year to year. The extreme winter of 1978-79 put down 10 snows in excess of 4 inches and a season total of 89.7 inches.
Dear Tom,
What are the extremes for Chicago's average annual temperatures? Any sign the average is rising due to global warming?
Robert Roschke, Chicago
Dear Robert,
In 138 years of official data, Chicago's average annual temperatures have ranged from 45.3 degrees (1875) to 54.5 degrees (1921). The trend of temperatures has been upward, but it's difficult to draw conclusions because the observation site has been relocated several times and each move disrupted the climatological continuity of the temperature record.
However, 80 years of data (1929-2008) from a single location -- Midway Airport -- indicate a warming trend, probably due more to a strengthening urban heat island effect than to global warming. Annual temperatures rose from 50.6 degrees during the first half of the period (1929-1968) to 51.2 degrees during the second half (1969-2008).
Dear Tom,
With winter approaching, how soon can we expect temperatures to drop below
zero?
Myra Weisbach
Dear Myra,
Chicago¹s earliest encounter with subzero weather took place nearly 60 years ago on the frigid Thanksgiving morning Nov. 23, 1950 when the mercury plunged to 1 below. The next day was even colder, with a low of minus 2 degrees. Subzero cold that early in the season is unusual, with the bulk of the city¹s negative temperatures occurring from mid December through mid February. The frigid season in Chicago peaks during February¹s opening days, a time of year that coincides with the winter¹s most persistent snow cover. Early March usually marks the end of below zero weather, though the 1 below zero reading on March 22, 1888 is the latest on record. Last winter Chicago logged 10 below zero days--the coldest was a minus 18 on Jan. 16.
Dear Tom,
If I throw a bucket of water from a hot air balloon at say 15,000 feet, will this water appear as rain drops or as big globs when it approaches ground level?
Don Sadecki, Westchester
Dear Don,
You'll get raindrops at the ground. Larger drops fall faster than smaller ones, but drop size has an upper limit. It's a matter of drop stability.
German physicist Dr. Philipp Lenard made the first accurate measurements of raindrop sizes, shapes and fall speeds around 1900. He found that raindrops can attain sizes no greater than one-fifth inch in diameter; they become unstable and shatter at larger diameters, and the largest drops fall at about 20 mph.
As a large raindrop falls faster and faster, the friction of its passage through the air causes it to flatten, then to bulge upward in the middle rather like an inverted paper bag, and finally to shatter into smaller drops that fall more slowly.
Dear Tom,
What is Chicago's longest string of daily lows at 10 degrees below zero or lower? What about zero or lower? And what is our longest string of highs 90 degrees or higher? What about 100 or higher?
Lou Liebovich, Hoffman Estates
Dear Lou,
Computer scans of three data sets -- Chicago's official temperatures (1871-2009) and data from Midway Airport (1928-2009) and O'Hare International Airport (1959-2009) --provide the answers. Chicago's longest string of days with low temperatures of 10 degrees below zero or lower is 7 days (Jan. 14 to 20, 1994); zero or lower: 10 days (Jan. 4 to 13, 1912, and Jan. 2 to 11, 1979); highs at or above 90 degrees: 12 days (July 6 to 17, 1936). That 90-degree string also included the city's longest string at or above 100 degrees: a sweltering 8 days (July 7 to 14, 1936.
Dear Tom,
My 5-year-old asks when the dinosaurs disappeared and if weather was the cause.
Jennifer Krause
Dear Jennifer,
Five major "life extinctions" have occurred on Earth, one of which ended the reign of the dinosaurs about 65 million years ago (though recent evidence suggests some dinosaurs survived and today's birds are descended from them).
A widely accepted theory to explain the dinosaur extinction draws together information from a variety of independent investigations. An asteroid estimated to be 6-10 miles in diameter crashed into Mexico's Yucatan Peninsula. The impact threw a massive amount of debris into the atmosphere, and heat generated as it rained down planetwide caused much of Earth's vegetation to burn. Volcanic eruptions elsewhere contributed additional atmospheric dust, and temporary global cooling hastened the dinosaur extinction.
Dear Tom,
On Nov. 11, 1911 Springfield. Missouri experienced a huge temperature drop attributed to a "Great Blue Norther." Can you elaborate?
Les Herbst Lake Villa
Dear Les,
A "Blue Norther" is a fast-moving cold front accompanied by a strong north or northwest winds, a dark blue-black sky and a large, rapid temperature drop. Such was the case on Nov. 11, 1911 in Springfield, Missouri when the cold front passed. Earlier in the day, with clear skies and brisk south winds, the temperature soared to a record high of 80 degrees. Around 3:30 p.m. dark
ominous clouds rapidly approached followed by an abrupt wind shift to the northwest. Sustained winds of 54 mph and gusts to 74 mph damaged numerous trees and houses. Temperatures plunged, falling to 13 degrees by midnight, setting a record low for the day. Nearly a century later the record low still stands, but the 80 degree high was equaled in 1989.
Dear Tom,
With the holidays approaching I remember a big Thanksgiving Eve snowstorm that probably was in the middle 70s. What year was that?
Ray Consentino, Homer Glen
Dear Ray,
The storm you remember took place on Nov. 26-27, 1975. The snow began Wednesday afternoon and fell with increasing intensity throughout the evening rush hour. The heavy snowfall clogged highways and canceled flights paralyzing holiday travel. Snowfall that Wednesday totaled 7.5 inches, and when the snow finally ended on Thanksgiving morning the city's official site at Midway Airport had logged 8.6 inches of snow. On Thanksgiving morning the snow was eight inches deep, tying 1895 for the city's deepest Thanksgiving snow cover. Just five years ago, another traffic-snarling Thanksgiving Eve snowstorm dropped 4.3 inches on Nov. 24, 2004.
Dear Tom,
My family visited Glacier National Park in July and a park ranger said the glaciers were in retreat. Could you provide more information?
The Stein family, Chicago
Dear Stein family,
U.S. Geological Survey researchers are carefully monitoring the disappearance of glaciers and snowfields in Glacier National Park and they indicate that it is occurring quickly.
One report, prepared in 2008, says, "Glaciers don't respond to anything else except climate change, unlike, for example, forests that can adapt. ... In 1850 there were an estimated 150 alpine glaciers of 25 acres or larger (in the park). Now there are only 25 glaciers left. By 2030, computer models suggest that all the remaining glaciers and snowfields will be gone."
Park snowfall has increased 10 percent in the past 50 years, researchers say, but higher temperatures and melting have overwhelmed the heavier snows.
