The preliminary data for October indicates that Illinois received an average of 3.2 inches of precipitation across the state. That is close to the long-term average of 3.26 inches.
The first map shows the distribution of the precipitation across the state. Most of this precipitation fell in the last few days of the month. The heaviest amounts were in Cook, Will, and Kankakee counties along with some areas in far southern Illinois. The largest monthly total so far is 6.79 inches at Bourbonnais.
Below the first map are two more lower-resolution maps showing the precipitation totals and percent of average maps. While the first map is based on both radar and surface observations, the remaining maps are based on surface observations only.
Finally, we have the snowfall map for October that shows the measurable snowfall across northwest Illinois. Many places across northern and central Illinois saw snow flurries in October.
The highest monthly snowfall total was at Mendota with 3.5 inches. [I am going to strike this from the posting because of some inconsistencies in their report]. Several sites in the northwest part of the state reported 1 to 2.5 inches of snow for October.