One of the impacts of the warmer-than-average weather in October and November is that soil temperatures have been slow to fall below 50 degrees . This is the important temperature threshold for those applying fall fertilizer (55 degrees with an inhibitor).
You can track daily soil temperatures from the Illinois Climate Network site: http://www.isws.illinois.edu/warm/soil/
As of this writing (November 13), yesterday’s daily high soil temperatures at 4 inches were still ranging from 49 degrees in the north to 58 degrees in the south. Naturally, the air temperatures are going to have to get into the 40s and stay there for these soil temperatures to continue to drop. However, the NWS forecast for the coming week shows highs in the mid to upper 50s in the north and in the low 60s in the south.
Here are the average dates from a publication released in 2004, The Climate Atlas of Illinois. According to those figures, we are behind schedule this year for seeing those soil temperatures cool off.