textproduct: Central Illinois

KEY MESSAGES

- Comfortable and dry weather is anticipated through Saturday, followed by the return of summer-like heat early next week.

DISCUSSION

Issued at 117 AM CDT Thu Aug 27 2026

Surface analysis early this morning shows an occluded low centered over southeast Ontario with a cold front stretched southward through the eastern Great Lakes Region and arching back westward through the Ohio Valley. Further northwest, an expansive area of high pressure is noted over the Plains states/Upper Mississippi Valley. This will expand east-southeast into the Midwest states today, keeping things comfortable and dry the next several days. High temperatures through Saturday will be seasonable in the low to middle 80s, with cool overnight lows in the 60s.

Strong upper ridging noted over the western US late this week will shift east this weekend, raising mid-level heights to around 590-594 dm by Sunday. Southerly return flow at the surface will bring a big push of a warmer and more humid air northward. High temperatures look to peak in the upper 80s to low 90s beginning Sunday with heat indices in the upper 90s to around 100 degrees as early as Monday. The Extreme Forecast Index has high values (0.8-0.9) paired with a Shift of Tails of 1, implying there is relatively high confidence in an anomalous late summer heat event occuring. Although high temperature records will be out of reach, record warm lows in the 70s could be tied or broken during this stretch.

Simultaneously, a northern stream shortwave trough will lift from the northwest US into the southern Canadian Prairies early next week, sending a cold front sagging southward from the Plains states into parts of the Midwest. Although a vast majority of the precipitation associated with the front looks to remain north of here, it will be highly dependent on the depth and strength of the trough. As of now, there is at least a low chance for showers and storms clipping northern parts of the forecast area Monday through Wednesday. Further south, mostly dry conditions are favored over the next 7 days.

AVIATION /06Z TAFS THROUGH 06Z FRIDAY/

Issued at 1206 AM CDT Thu Aug 27 2026

High pressure currently over the northern Great Plains will shift to the Upper Midwest by late in the period. A modest northwest breeze will be in place across central Illinois during the day Thursday, but winds are expected to go light and variable after sunset as the ridge axis moves overhead. Diurnal cumulus forming Thursday morning may briefly result in MVFR ceilings, but VFR conditions are otherwise favored through the period.

ILX WATCHES/WARNINGS/ADVISORIES

None.