National Weather Service United States Department of Commerce
 

Normal chances of a White Christmas. Image from Illinois State Water SurveyAcross Illinois, there is normally a wide range in White Christmas chances. A White Christmas is defined as having at least 1 inch of snow on the ground Christmas morning. As one might expect, chances increase the further north you go across the state. Across the northern third of the state, odds are generally in the 40-60% range, with 20-40% in central Illinois, and 25% or less in the southern parts of the state.

Here in Illinois, a widespread snow cover has been hard to come by the last several  years. The loop below, from the National Centers for Environmental Prediction, show the snow cover across the contiguous United States on Christmas Morning since 2010. That particular year (2010) was the last time there was a rather solid snow cover on Christmas morning across the entire state, though parts of the state had a snow cover in 2012, 2013, and 2016. 

Christmas Day snow depth since 2010

Specific Christmas Day climate statistics are available for Peoria and Springfield