August was cool and dry for most of Illinois. The statewide average temperature was 70.6 degrees, 3 degrees below normal, and the 12th coolest August on record. This followed June and July which were both slightly above normal. The warmest daily reading in Illinois for August was 96 degrees, reported at Effingham on the 21st. The coolest daily reading in Illinois was 42 degrees, reported at Shabbona (DeKalb County) on the 25th.
The statewide average precipitation was 2.41 inches, 1.18 inches below normal. There was a narrow band of 3 to 6 inches between Quincy to just north of Champaign. The rest of the state received 1 to 3 inches, which was 1 to 3 inches below normal. The highest monthly total for August was 7.09 inches, reported at both Augusta and Hoopeston. On a side note, conditions in northern Illinois were quite different than July when that area was particularly wet. Click to enlarge.
Summer (June, July, August)
The statewide average temperature for summer was 73.1 degrees, 0.5 degrees below normal. The statewide average precipitation for summer was 10.18 inches, 1.69 inches below normal. Here are the Midwest precipitation totals, departures from normal, and percent of normal, in that order. Much of the Midwest experienced a fairly wet summer with the only large dry spots showing up in Iowa and Illinois, and smaller areas in northern Minnesota and southern Michigan. Click to enlarge.
What About September?
The NWS outlook for September shows a continuation of the type of weather in August. Illinois and much of the eastern half of the US has an increased chance of being cooler than normal. Most of Illinois has an increased chance of being on the dry side, as does most of the western half of the Midwest and the Plains states. Far southeastern Illinois has an increased chance of wetter than normal conditions. In fact, they are getting a piece of what’s left of Hurricane Harvey today.