The mild winter weather is not expected to last in Illinois, but you probably already knew that.
How mild has December been? As of December 18, the statewide average temperature for December stands at 34.3 degrees, 2.1 degrees above average. Precipitation (both rain and the water content of snow) stands at 1.13 inches. Areas north of I-70 are much drier with amounts closer to half an inch, while south of I-70 amounts of 1-4 inches are common. At this point there has been very little snow in December, although that is about to change soon.
The latest NWS outlooks for January and the rest of winter are shown below (click to enlarge).
The temperature forecast for both January and the January-March period show almost all of Illinois with a higher chance of below-average temperatures. Only far northern Illinois escapes this forecast. On the other hand, precipitation has a higher chance of being below average across Illinois and the Great Lakes region. In most cases, these long-range forecasts only nudge the temperature by a few degrees. So, there is still little sign that this winter will be as severe as last.
The NWS does not issue a winter snowfall forecast. And, a combination of colder temperatures and less precipitation does not always translate into less snow. Many times colder weather produces lighter fluffy snow that accumulates but has less water content. We saw a lot of that last winter. However, even if this forecast of colder and drier conditions captures the overall pattern of this winter, we could still see some significant winter storms. Be prepared.