August: 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 and the 12th wettest August on record.
The warmest daily high temperature was 97 degrees reported at Chicago Botanical Gardens (8/5), Chicago O’Hare (8/4), Jerseyville (8/7), and Pittsfield (8/29). The coolest reading was 42 degrees reported at Rochelle (8.22).