The statewide average precipitation for August was 1.38 inches, according to State Climatologist Jim Angel, Illinois State Water Survey, Prairie Research Institute, University of Illinois. It was the third driest August on record and 2.22 inches below the 1981-2010 average.
The driest August in Illinois was in 1952, with only 1.12 inches of rain. Even though last year was remembered for the severe drought, the August 2012 precipitation was 3.64 inches, which was 0.04 inches above average.
The only areas with significant precipitation this August were far southern Illinois and a portion of northeastern Illinois. Elsewhere, precipitation amounts were far below average. A few areas in western Illinois received less than 0.1 inches.
The statewide average temperature for August was 73.1 degrees F., which is only 0.4 degrees below average. August was noteworthy for being much below average for the first half of the month and much above average for the latter half, effectively cancelling each other out by the end of the month.
The statewide average precipitation for summer (June, July, and August) was 9.93 inches, which is 1.92 inches below average. While June was above average (5.41 inches), both July (3.14 inches) and August (1.38 inches) were below average. It was an improvement over last summer when the average precipitation for the summer was 6.92 inches, 4.93 inches below the 1981-2010 average.
The statewide average temperature for this summer was 72.5 degrees, 1.1 degrees below the 1981-2010 average. June, July, and August were all below average but July had the coolest departure of 2.4 degrees below average.
The statewide average precipitation for 2013 so far was 33.48 inches, which was 6.0 inches above the 1981-2010 average. This was far higher than last year when the statewide precipitation was only 17.79 inches through the end of August–an amount almost half of this year’s precipitation.
The statewide average temperature for 2013 so far was 46.3 degrees, which was 1.2 degrees below the 1981-2010 average. This was far cooler than last year when the statewide temperature was 52.7 degrees, 5.2 degrees above average.