The statewide average temperature for December 2011 in Illinois was 35.7 °F, 5.9 °F above average. This ranked as the ninth warmest December on record with statewide records going back to 1895. The highest temperature for the month was 67 °F at Cairo on December 5. The lowest temperature was 0 °F at Monmouth on December 10.
The statewide average precipitation for December in Illinois was 3.43 inches, 0.74 inches above average or 127 percent of average. The highest precipitation total for the month was Brookport Dam (along the Ohio River) with 7.70 inches.
Snowfall totals for December were much below average across the state. The highest snowfall total for the month was at Stockton (far northwestern corner of Illinois) with 4.0 inches. This stands in stark contrast with December 2010 when the highest snowfall total was at Galena with 30.0 inches.