Summary: So far in December temperatures have been 5.6 degrees above normal, while the statewide average precipitation has been 0.28 inches, a tenth of normal. The NWS released their outlook for the rest of this winter. Colder than normal conditions are favored in Illinois in January. Colder and wetter conditions favored in January through March. Wetter conditions favored for most of Illinois in April through June.
What are the historical chances of a White Christmas?
We define a “white Christmas” as having at least an inch of snow on the ground on December 25. The map below shows the odds across the state. It should come as no surprise that the highest odds are in northern Illinois. In general, the odds are about 40-60 percent in the northern third of Illinois, 20-40 percent in central Illinois, and 0-20 percent in southern Illinois.
There can be large differences between nearby sites. Snowfall is notoriously difficult to measure with blowing, drifting, and melting. Two nearby sites may have different results due to exposure to the sun and the wind as well as the dedication of the observer to report on Christmas Day.
What happened last year?
The preliminary numbers are in for Illinois and November was slightly cooler and drier than normal.
The statewide average temperature for November was 41.7 degrees, 0.8 degrees below normal. The warmest reading in the state was 79 degrees at Belleville on November 2. The coldest reading in the state was 11 degrees at Stockton on November 24.
The statewide average precipitation was 2.13 inches, 1.34 inches below normal. The largest precipitation amount was 5.60 inches at Paxton. Some snow was reported in northern and central Illinois. The largest snowfall amount was 1.5 inches at the Chicago Botanic Garden.