Lows of 31-35 are likely tonight with frost & freezing in the area.
Note the white freezing (32) line below.
It will turn cloudy rapidly tomorrow morning with a wave of cold light rain generally 11 a.m. to 6 p.m.
Yes, it could begin as a period of all snow in central Illinois! Brief dusting/whitening on the grass is possible in places there. Here, given so much dry air aloft & cold temperatures aloft, I cannot rule out a flakes briefly mixing in here. If the precip could get in here earlier, then we could have a period of light snow.
After dry weather through morning & brief highs of 42-47, evaporative & dynamic cooling with the light precipitation will result in temperatures falling to 36-40 in the afternoon! Temperatures will be in the 30s for the Frenzy, but the light rain/flakes should exit by 6 p.m.
As skies clear tomorrow night, we will drop to 31-35 with frost.
After a dry Saturday with 50s, clouds will increase Sunday with some cold rain showers late Sunday to Monday as the remnants of Sergio pass south of us. That is where the bulk of the rainfall will occur. Highs Monday should run in the 40s. Note the accumulating snowfall from Kansas to the Panhandle of Oklahoma & Texas.
Overall rather dry & chilly weather will dominate through October 27 with temperatures as much as 20 degrees below normal at times. No stormy, very wet weather is expected up to that point. Many nights will reach the 20s & 30s, however. The leaves will shift to their autumn hues very rapidly.