textproduct: Central Illinois

KEY MESSAGES

- There is a low risk for severe storms Wednesday evening, with damaging winds as the main threat. SPC has a Marginal Risk (level 1 of 5) for severe weather west and northwest of a St Louis to Watseka line Wednesday.

- Hot and humid weather returns early next week with heat index values approaching 100 degrees, though passing storm complexes could occasionally temper the heat.

DISCUSSION

Issued at 235 AM CDT Tue Aug 4 2026

Dry weather is expected through tonight as a high pressure lingers over the region. Highs in the 80s and low in the 60s will be in place for the week. Temperatures look to near or rise above 90 degrees for highs by Sunday into the new week, with increasing humidity. The LREF shows a 50-80% chance of apparent temperatures being greater than 95 degrees on Monday afternoon and 50-70% chance on Tuesday afternoon across the entire forecast area. The CPC has both the 6-10 and 8-14 day outlooks with 60-80% chance of above normal temperatures, so the sweltering weather isn't over quite yet for this summer. This is said with the caveat of if we get some widespread thunderstorm activity next week, the heat indices may not be able to achieve 95-100+ degrees.

A more active pattern will return late tonight as a cold front pushes into the state by tomorrow. There is some discrepancies in the CAMs with the timing of the earlier round of showers and thunderstorms. The HRRR has the activity entering the western CWA by 10z, whereas the NAMNest has it entering by 15z. It looks to be that there will be multiple rounds of showers and storms from Wednesday morning to Thursday afternoon. MUCAPE values (and similarly SBCAPE values) are still looking to be around 1500-2500 J/kg and bulk shear values of 30-40 knots. SRH values look to be around 200-300 in the vicinity of the activity. The SPC has a marginal risk (level 1 of 5) in place for Wednesday west and northwest of a St Louis to Watseka line. If any severe weather occurs, it looks like conditions are best from mid afternoon into the early evening Wednesday. All hazards are in play, with the main concern being damaging wind gusts. Overnight, the severe threat should wane without the daytime heating effect. WPC does have a slight risk ERO in place for nearly the same area as the SPC outlook. The CAMs are hinting at some training over the same areas on Wednesday into Thursday. We will need to monitor for a flash flooding threat.

The front is appearing more likely to linger over the area beyond Wednesday, keeping us in a more active pattern through late week. Thursday has a very similar environmental look in place, especially over west/southwestern IL, in the afternoon. Each day, from Thursday to Monday, could see some low risks for severe weather based off a coarse look at thermodynamics in place and a look at the machine learning models. We will continue to monitor the showery and severe thunderstorm possibilities beyond Thursday morning as we move forward in the week.

AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/

Issued at 1242 AM CDT Tue Aug 4 2026

Mostly clear skies are expected for the upcoming 24 hours, although patchy fog and slightly reduced visibility are expected in the early morning from around 09Z-13Z. Winds light and variable, becoming S 4-8 kts by 16Z. Winds light and variable again after 00Z.

ILX WATCHES/WARNINGS/ADVISORIES

None.