Jul 02 | Climate Review and Weather Update

by Trent Ford, State Climatologist
ISWS PRI University of Illinois

Temperatures this week packed a punch, ranging from the high 70s in northern Illinois to the low 80s in southern Illinois, between 1 and 4 degrees above average. This week featured our first real summer heat wave across the state, as high temperatures reached into the mid 90s, with very high humidity pushing peak heat index values well over 100. However, that persistent humidity and very warm nights were the truly remarkable feature of this heat wave. Chicago saw more than 60 consecutive hours with heat index values over 80 degrees, creating some stifling nighttime weather.

The ridge that brought us the heat also mostly kept rainfall away this week. 7-day totals ranged from virtually northing in the Quad Cities to just under 4 inches in southeast Illinois. The relatively dry end to June was quite a contrast to the month, which ended up being a top 5 wettest June on record statewide, and the 3rd wettest on record in both Bloomington-Normal and Galesburg. The calmer, albeit hot weather also brought us a 5 day stretch without any storm reports in Illinois, which was the longest such stretch in the state since May.
Looking ahead, the heat, and likely that storm report streak, will both come to an end as we move into the weekend. The ridge will move east and behind it will come a more disturbed pattern with highs in the 80s and more frequent chances of thunderstorms and showers. The latest 7-day forecast from

National Weather Service has the northern half of the state picking up between a half inch and 2 inches, while southern Illinois will likely see mostly less than half an inch this upcoming week. Farther out, the outlooks for mid-July show slightly higher chances of warmer weather coming back, with best odds of wetter than normal weather, too. Look for that disturbed, warmer and stormy weather to appear off and on throughout this, the climatological hottest month of the year in Illinois.