Wet August Wraps Up Cool, Wet Summer in Illinois

Highlights: The 12th wettest August in Illinois finishes out the 10th wettest summer on record. While August was slightly warmer than average, the summer was cooler than average. Here are the statistics.

August Statistics

The statewide average precipitation for August was 5.18 inches, 1.59 inches above average and the 12th wettest on record. The wettest area of the state was Cook County. The largest monthly total was from a CoCoRaHS site (IL-CK-100) in Cicero with 10.20 inches of precipitation.

This first map shows several areas across the state with amounts of 7 to 10 inches (oranges and reds), according to radar estimates. There were a few areas in the northwest and east-central Illinois with only 2 to 3 inches. The second map shows the departures from average, showing the many areas with 2 to 8 inches above average for the month.

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The statewide temperature for August was 73.9 degrees, 0.3 degrees above the 1981-2010 average.The first half of August was exceptionally cool, like July, with temperatures about 3 degrees below average. The second half of August was much warmer, with temperatures about 3 degrees above average. The result was a near-average August.

Summer Statistics

The statewide average precipitation for summer was 14.96 inches, 3.09 inches above average and the 10th wettest summer on record. The wettest summer was 1993 with 18.51 inches.

For the three summer months of June, July, and August, the statewide average temperature was 72.4 degrees, 1.2 degrees below average and the 30th coolest summer season on record. The milder August knocked this summer out of the running for one of the coolest on record. That is not necessarily bad from an agricultural point of view, the warmer August helped to keep crops on track for maturing this fall.

Monthly Temperature and Precipitation Departures from Average

The outstanding colder-than-average months for 2014 were January, February, March, and July. The rest of the months have been near-average.

The second plot shows monthly precipitation departures alternating between dry and wet months. Based on this pattern, one would be tempted to predict that September will be drier than average.

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