textproduct: Central Illinois

KEY MESSAGES

- Dangerous heat and humidity will peak today and Monday, pushing heat index values between 105F and 115F, especially west of Interstate 55.

- Multiple thunderstorm complexes (MCSs) moving around the region today and Monday present a conditional threat for severe weather and heavy rain while potentially disrupting daytime heating.

- A cold front will gradually push south through the region Tuesday, bringing relief from extreme heat and transitioning the pattern to near-normal temperatures with storm chances returning by late week.

Tuesday through Saturday

The cold front is modeled to push slowly southward across central Illinois on Tuesday, initiating a gradual airmass transition. However, heat and humidity will be slow to scour out completely, with dewpoints remaining in the lower 70s across southeast Illinois through Tuesday afternoon. High temperatures Tuesday will top out in the upper 80s to near 90F.

From Wednesday through the remainder of the week, the upper- level pattern transitions to classic summer northwest flow on the eastern flank of the retrograding central US ridge. While the extreme thermodynamic profiles will ease, northwest flow regimes in late July notoriously support ridge-riding shortwaves and MCS activity. Expect temperatures and humidity to settle back to near-seasonal norms (highs in the upper 80s, heat indices in the mid-90s). Periodic storm chances will persist throughout the extended period, with ensemble guidance showing high consistency for a more defined shortwave trough to dig across the Mid-Mississippi Valley around Friday.

AVIATION /12Z TAFS THROUGH 12Z MONDAY/

Issued at 500 AM CDT Sun Jul 26 2026

Low stratus and patchy fog will persist through late morning in the vicinity of a surface warm front. Clouds and fog will gradually lift and mix out between 15z-18z, with VFR conditions prevailing thereafter and holding through the remainder of the TAF period.

Confidence and coverage of showers and thunderstorms remains too low to include in the regional TAFs today, though a PROB30 group for TSRA has been added at KCMI near the end of the TAF period (Monday morning) to reflect a growing trend in guidance for a nocturnal thunderstorm complex to dive southward into eastern Illinois.

Surface winds will generally remain light and from the south today.

ILX WATCHES/WARNINGS/ADVISORIES

Extreme Heat Warning from noon today to 9 PM CDT Monday for ILZ027>029-036-037-040>042-047>052. Heat Advisory from noon today to 9 PM CDT Monday for ILZ030- 031-038-043-044-053-054-061-066-071-072.