textproduct: Central Illinois

KEY MESSAGES

- Unseasonably warm temperatures in the 80s stick around through midweek, especially near and south of Interstate 72.

- Rain chances increase late tonight into Wednesday over west-central Illinois. Widespread heavy rain is then expected Thursday through Friday with a 50-90% chance of exceeding 1 inch north of Interstate 70.

- Drier, autumn-like conditions move in late Friday into Saturday, dropping weekend highs into the upper 60s to low 70s.

DISCUSSION

Issued at 131 PM CDT Tue Sep 29 2026

Surface analysis early this afternoon shows a large area of high pressure centered over the Mid-Atlantic states with southerly flow stretched from the southern Plains into the Upper Midwest. Temperatures will remain unseasonably warm through midweek for most, with highs peaking in the upper 70s to low 80s areawide this afternoon, then topping out in the upper 70s to 80s near/south of I- 72 Wednesday and Thursday.

Tropical moisture stemming from Hurricane Polo will get lifted northward through the central US then spill into the middle Mississippi Valley beginning tonight, bringing likely chances for rain showers to areas north of a Quincy to Bloomington line through Wednesday afternoon. More widespread shower and occasional storm chances will impact the entire area Thursday into Friday as a cold front pushes the tropical moisture further southeast through the region. Climatologically high PWATS (up around 2 inches) and warm cloud processes will support pockets of heavy rain, with areas near and west of the Illinois River expected to receive the highest amounts. The National Blend of Models (NBM) shows a 50-90% chance of exceeding 1 inch of rain north of I-70 through Friday with a 50-70% chance of exceeding 2 inches north of a Jacksonville to Bloomington line. This may lead to localized flooding and rises on area rivers, streams, and creeks where the heaviest rain occurs.

High pressure settles into the Midwest states behind the cold front later Friday into Saturday, bringing a period of more seasonable temperatures and drier weather through at least early next week.

AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 1212 PM CDT Tue Sep 29 2026

VFR conditions are expected through the TAF period. Southerly surface winds will back to the southeast this evening before returning to the south Wednesday morning. Clouds will lower overnight ahead of an approaching system, with scattered rain showers expected at KPIA, KBMI, and possibly KSPI by morning.

ILX WATCHES/WARNINGS/ADVISORIES

None.