textproduct: Central Illinois

KEY MESSAGES

- Some showers and thunderstorms are still moving across central and southeastern IL early this morning as a cold front pushes south. Behind the cold front, a weak high pressure center will build over the Midwest later today into tomorrow. - A persistent northwest flow will keep temperatures and humidity levels in check the next several days, with seasonable highs in the upper 70s to mid 80s and lows in the upper 50s to 60s.

DISCUSSION

Issued at 209 AM CDT Thu Aug 20 2026

Earlier in the night, there was some considerable flash flooding that occurred north of I-72. Some showers and thunderstorms are still moving across central and southeastern IL this morning but the flash flooding threat appears to have ended. Heavy rain is still possible in the stronger showers as this cold front exits off to the south this morning.

Behind the cold front, a weak high pressure center will build over the Midwest later today into tomorrow. Today is looking to be quite pleasant. There could be some sprinkles/light rain in south central IL this afternoon, but rainfall amounts should be minimal. Friday there is a 20-40% chance of additional showers, perhaps some thunder too, area wide as a weak upper disturbance passes overhead.

After Friday, a primarily dry forecast is on deck through early next week, with temperatures in the upper 70s to 80s for highs and upper 50s to 60s for lows.

AVIATION /12Z TAFS THROUGH 12Z FRIDAY/

Issued at 452 AM CDT Thu Aug 20 2026

Patchy fog is ongoing across central IL this morning and should remain out of the TAF sites. MVFR ceilings are possible at time through 14-15z this morning. After that, VFR conditions will reign for the remainder of the 12z period. By 00z, winds become light and variable for the evening and overnight.

ILX WATCHES/WARNINGS/ADVISORIES

None.