textproduct: Central Illinois

KEY MESSAGES

- Dry and cool weather is expected on Thursday with daytime highs in the upper 60s to near 70 degrees.

- Widespread rain returns Friday with occasional chances for showers and storms continuing through early next week.

- Temperatures steadily climb through next week with highs in the middle to upper 80s expected by next Tuesday and Wednesday.

DISCUSSION

Issued at 122 PM CDT Wed May 20 2026

A cold front is positioned near the Ohio Valley early this afternoon with high pressure centered over the western Great Lakes Region. Shortwave energy gliding across the cold front has kept scattered showers in place near and south of I-70 up to this point today with the chance continuing for at least a couple more hours before pushing east of here. Cloud cover will be slower to clear overnight, especially in southeast Illinois where overnight lows will hold in the middle 50s. Further north and west where skies will clear quicker and some influence from a lake breeze is felt, lows are expected to drop into the middle to upper 40s.

High pressure centered to our north will keep things dry and cool on Thursday with highs peaking in the upper 60s to near 70 degrees. An upper trough will shift into the central US late this week, bringing a wetter pattern back to the area. Several shortwave impulses will track through the middle Mississippi Valley ahead of the main trough, with the first bringing widespread rain on Friday as a warm front lifts north. There remains a lot of spread in potential rain amounts for Friday with the National Blend of Models (NBM) showing anywhere from just a couple tenths of an inch in west-central parts of the state to upwards of 1 inch in southeast Illinois. Coverage of activity will dictate rainfall amounts, though high PWATS up around 1.5 inches would support higher rainfall rates, especially in any storms. Isolated storm chances look to be focused in east-central and southeast Illinois where a narrow ribbon of instability is shown. Additional chances for showers and storms are possible Saturday and Sunday, though dry periods are likely on both days.

The upper trough lifts into Ontario early next week as high pressure ridging builds over the central US in its place. An upper low on the equatorward side of the high will become trapped over the south-central Plains, resulting in a Rex block setup by midweek. Temperatures will steadily climb this weekend into next week, soaring back into the 80s by Tuesday and Wednesday. A feed of Gulf moisture lifting into our area out ahead of the upper low could promote more shower and storm activity through the early to middle parts of next week. Although thunderstorms appear likely at times, weak upper support should largely mitigate the threat for severe weather the next 7 days.

AVIATION /18Z TAFS THROUGH 18Z THURSDAY/

Issued at 1211 PM CDT Wed May 20 2026

MVFR ceilings may impact KDEC and KCMI for a couple more hours this afternoon before clouds lift as high pressure settles southward over the area. North-northeast winds with speeds between 10-15 kts will continue to veer, becoming easterly by Thursday morning.

ILX WATCHES/WARNINGS/ADVISORIES

None.