December 2010 in Illinois – Cold and Snowy

December 2010 in Illinois turned out to be one of the coldest and snowiest on record. I updated the numbers on January 3 and the maps on January 5.


The average statewide temperature was 24.0 degrees, 5.8 degrees below normal and the 12th coldest on record, based on preliminary data.


Snowfall was above-normal throughout the state in December and heaviest in a band from northwest Illinois into east-central Illinois (see maps below). Snowfall totals for December include 20.4 inches in Champaign-Urbana (snowiest December on record), 18.1 inches in Bloomington-Normal(second snowiest December on record), and 19.2 inches in Peoria (third snowiest December on record). Champaign-Urbana beat both Rockford (19.2 inches) and Chicago O’Hare Airport (16.2 inches) on snowfall totals. The largest snowfall total reported in the state was 30.0 inches near Galena by a CoCoRaHS observer. Streator reported 28.5 inches, the highest amount from a NWS cooperative observer.


Even though snowfall was above average in most locations, the average statewide precipitation was 1.8 inches, 0.9 inch below normal. Some of the snowfall did not have a high water content, especially if it fell when the temperatures were in the 20s. While the rule of thumb is that 10 inches of snow equals 1 inch of water, a  10 to 1 ratio, I have seen ratios ranging from 4 to 1 to 22 to 1 in Illinois.


December 2010 snowfall
The December 2010 total snowfall in inches.
December 2010 snowfall departure in Illinois
The December 2010 snowfall departures (inches) in Illinois.