textproduct: Central Illinois

This forecast discussion was created in the public domain by the National Weather Service. It can be found in its original form here.

KEY MESSAGES

- Welcomed relief is in store for today and Monday, with high temperatures in the 80s for most locations and dropping heat indices into the 80s, near 90.

- High heat and humidity return Tuesday and Wednesday. Wednesday looks to be the hottest, bringing another risk for triple- digit heat index values. There is a 20-30% chance of heat indices greater than 100 degrees south of I-70 Wednesday afternoon.

DISCUSSION

Issued at 134 AM CDT Sun Sep 6 2026

A backdoor cold front pushed into the area yesterday evening, which will bring "relief" today and Monday, where heat indices will be in the mid 80s to near 90 and highs in the 80s to low 90s. These cooler temperatures will warm back up to low to upper 90s by Tuesday and Wednesday as the upper ridging builds back eastward once again. There is a 20-30% chance of heat indices greater than 100 degrees south of I-70 Wednesday afternoon, from the LREF.

A weak cold front will move through on Wednesday as the ridge gets broken down by an upper low, potentially stalling out across IL. It will bring another two day break from the sweltering mid to upper 90 temperatures, dropping temperatures into the low to mid 80s before building back to near 90 for the weekend.

The next chance for any rain will come Thursday with the greatest POPs (50-70%) mainly near and south of I-72. A strengthening LLJ will reinvigorate thunderstorm development along the stalled boundary. As of now, the machine learning models are not showing a severe threat with these storms. The PWATs look to be around 1.8-2.2 inches and WPC has a marginal risk for excessive rainfall for day 5 (Thursday).

AVIATION /12Z TAFS THROUGH 12Z MONDAY/

Issued at 557 AM CDT Sun Sep 6 2026

An area of low stratus is drifting south across the terminals this morning bringing MVFR/IFR ceilings and MVFR visibilities with it. All sites should scatter out and become VFR by 13-14z. CMI/BMI has scattered out now but may have periods of IFR ceilings, indicated with a TEMPO group. After that, VFR conditions and light eastern winds will linger into tomorrow morning, with the occasional gust to 10-12 knots.

ILX WATCHES/WARNINGS/ADVISORIES

None.

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