Aug 07 | Climate Review and Weather Update
by Trent Ford, State Climatologist
ISWS PRI University of Illinois
The first full week of August is in the books. The last month of summer has started a bit cooler and wetter. Average temperatures this week ranged from the low 70s in northern Illinois to mid-70s in southern Illinois, between 1 and 4 degrees below normal. High humidity limited how far nighttime temperatures could drop, but it also kept daytime temperature moderate. A few places had daytime highs in the 60s last week, including 69 in Rockford and Ottawa.
We were in a bit of a disturbed weather pattern this week, with multiple rounds of scattered storms that produced some big gradients in rainfall. 7-day totals ranged from around three quarters of an inch in west-central Illinois to nearly 5 inches in the Chicagoland area. Even with the wetter weather this week, most of the state has been 1 to 2 inches drier than average going back to the start of July, with the strong exceptions of Chicagoland, the St. Louis Metro East area, and far southern Illinois, which have been abundantly wet. Speaking of the Chicago area, the National Weather Service wrapped up its summary of the very strong storms that moved through northern Illinois on July 27th. The storms produced 7 tornadoes stretching from Glen Ellyn to Romeoville. Most impressive from that system was the non-tornadic straight-line winds, which exceeded 100 mph in some areas. This included a 104 mph wind gust measured in Monee, among the strongest wind gusts recorded in state history.
Looking ahead, a bit more summer-like heat will build in this weekend and early next week with highs in the upper 80s to low 90s, before a cold front moves through the middle of next week. Scatter storms will mill about the state this weekend, but likely not producing much total rainfall. However, more widespread storms and rainfall will accompany the mid-week cold front, bringing up to 1 – 4 inches of additional rain over the next 7-days. The highest totals are expected in northern and central Illinois, but virtually the entire state is expected to get at least 1 inch next week. The rain will be a good way to help finish out any late planted corn and give beans a last push of moisture as we head toward fall. Farther out, the outlooks continue to show mixed temperature patterns swinging between cooler and warmer than normal conditions in mid-August, but a wetter than average pattern at least through the third week of the month.