The statewide average temperature for the three winter months of December, January, and February in Illinois was 26.1 degrees, 7.5 degrees below average. While cold, it was not nearly as cold as last winter’s 21.7 degrees. This winter ranks as the 30th coldest on record.
This winter started off mild with an average December temperature of 33.9 degrees, 4 degrees above average. The average temperature in January was 25.7 degrees, only 0.7 degrees below average, and the average in February was 18.6 degrees, 12.3 degrees below average. See figure to the left, click to enlarge. Last winter, all three months were well below average.
Snowfall was above average for the winter from December through February. Most of that fell in February. December was snow-free for most of the state except in the far west. Snowfall was common in January but below average except for a band across northern Illinois. Major snows occurred in February to bring up the winter snowfall totals across the state. Above-average snowfall occurred across northern and western Illinois as well as far southern Illinois. The maps below show the observed amounts and departure from average.
The average precipitation for December-February was 4.97 inches, 1.85 inches below average. In fact, most of the Midwest received below-average precipitation this winter (figure left). Precipitation is a measure of both rainfall and the water content of any snow. While we received above-average snowfall, the water content of that snow was not always great. In a typical year we can get rain in winter, but not so much this winter. This kind of precipitation deficit would be a concern during the growing season. However, in winter the water demand is low.
Based on preliminary data, the Illinois statewide temperature for February was 18.7 degrees. That was 12.1 degrees below the long-term average and the seventh coldest February on record. No surprise there.
The statewide average temperature for the three core winter months of December, January, and February was 20.8 degrees. That was 8.2 degrees below average and the fourth coldest December-February period on record. Incidentally, it is in a 3-way tie with 1917-18 and 1976-77. The coldest winter was 1977-78 at 19.6 degrees. The winter of 1978-79 was in second place at 19.9 degrees. Overall, this winter was comparable to those in the late 1970s.
Below is the table of the ten coldest February’s on record for Illinois. It’s really hard to beat those cold February’s in the late 1970s. The 1981-2010 statewide average is 30.8 degrees.
Here are the ten coldest December-February periods in Illinois since 1895. The 1981-2010 statewide average is 29.0 degrees.
The snowfall for February was above average across the state. The total snowfall ranged from 4 inches in far southern Illinois to 15-20 inches in north-central Illinois. The snowfall departures from average ranged from 1-5 inches south of Interstate 70 and between 10 and 18 inches between Interstates 70 and 80.
The statewide precipitation for February was 2.28 inches. That was just 0.17 inches above average. Precipitation includes both rain events along with the water content of any snowfall. The result in February was that the above-average snowfall did not translate to above-average precipitation because several of those snowfall events occurred in colder conditions when snow density is lower (i.e, fluffier).
By the way, here are the snowfall totals for the entire snowfall season. You may recall that we saw snow flurries back in October and some measurable snow in November. Some of largest snowfall totals this winter are in the Chicago area and include Lincolnwood with 79.8 inches and Oak Park with 78.6 inches.