September was 1.5 degrees cooler than average and 0.88 inches wetter than average for Illinois. Year to date temperatures were 3.3 degrees below average and the 6th coolest January-September on record. The year to date precipitation was 32.91 inches, 2.5 inches above average.
The statewide average temperature for September in Illinois was 64.4 degrees, 1.5 degrees below the 1981-2010 average.
The statewide average precipitation for September in Illinois was 4.12 inches, 0.88 inches above average. The heaviest rains fell across western and central Illinois with amounts of 6 to 9 inches (map below). A second area of heavy rains occurred south of Interstate 70 near Effingham. The largest monthly total reported so far is Beardstown with 10.72 inches.
Precipitation departures from average for the month (below) show how widespread the above-average precipitation was across Illinois. The areas in blue and purple were 2 to 6 inches above average. Only far southern and far northern Illinois received less than average precipitation for September.
Year to Date (January – September)
The statewide average temperature for January-September was 52.3 degrees, 3.3 degrees below average and the 6th coolest January-September on record.
The statewide average precipitation for January-September was 32.91 inches, 2.5 inches above average and the 31st wettest January-September on record. Here is a map showing the precipitation departures for January-September.