Based on preliminary data, the statewide average precipitation in Illinois for October was 4.94 inches, 1.70 inches above normal and the 10th wettest October since 1895. The largest monthly total was 15.90 inches of precipitation in Glen Ellyn. Seven other sites in that area reported over a foot of precipitation.
The other noteworthy precipitation event of October was that several sites in northern and central Illinois reported seeing snow on October 28. In most areas, it was nothing measurable, just flurries. However, one station, New Lenox (Will County), did report 0.1 inches.
The statewide average temperature for October in Illinois was 57.7 degrees, 3.3 degrees above normal and the 21st warmest October since 1895. The first 21 days of October were about 7 degrees above normal and the last 10 days were 7 degrees below normal.
Many areas of the state dropped below freezing for the first time this fall. The coldest reading in the state was 19 degrees at Perry, IL, on October 29.
Here are the precipitation maps for October, showing the exceptionally wet areas in northeast Illinois and widespread amounts in the rest of the state.