Illinois was warmer and wetter than normal in August and in the summer

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[September 07, 2018]    The statewide average temperature for Illinois in August was 74.9 degrees, 1.3 degrees above normal. The statewide average rainfall was 5.25 inches, 1.66 inches above normal, according to Illinois State Climatologist Jim Angel of the Illinois State Water Survey at the University of Illinois.

The warmest daily high temperature was 97 degrees reported at the Chicago Botanical Gardens (Aug. 5), Chicago O’Hare (Aug. 4), Jerseyville (Aug. 7), and Pittsfield (Aug. 29). The coolest reading was 42 degrees reported at Rochelle on Aug. 22.

August was the 12th wettest August on record in Illinois. Rainfall was heaviest in the west and southern portions of the state with some areas 5 to 8 inches above normal. Meanwhile, parts of east-central and northeast Illinois had below-normal rainfall. The largest monthly total was in Arlington Heights with 10.22 inches.

In the summer (June, July, and August), the statewide average temperature was 75.0 degrees, 1.4 degrees above normal. The statewide average precipitation for the summer was 14.86 inches, 2.99 inches above normal and the 13th wettest summer on record.

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Rainfall was heaviest in the northwest and south with some areas reporting totals that were 6 inches or more above normal. Meanwhile, a few spots around the state were persistently dry, as in the area around Kankakee.

The largest summer rainfall total was 24.50 inches at Rockford. One of the lowest summer rainfall totals was 5.92 inches reported at Ashkum in Iroquois County, south of Kankakee. The rainfall total was about half the normal summer rainfall for that area.

[Lisa A. Sheppard]


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