textproduct: Chicago

KEY MESSAGES

- Increasing heat and humidity expected next week with periodic shower and storm chances.

DISCUSSION

Issued at 147 PM CDT Thu Aug 27 2026

Surface high pressure over the Great Lakes will maintain tranquil weather through Friday. Light winds overnight may lead to a brief period of patchy ground fog early Friday morning, primarily in interior northern Illinois. Otherwise, afternoon conditions on Friday remain comfortable with partly cloudy skies and high temperatures in the lower 80s.

A shifting upper-level pattern will bring building heat this weekend as a Rockies upper-level ridge expands eastward. Strong warm air advection and steepening lapse rates along its eastern periphery may trigger scattered showers and thunderstorms late Saturday into Saturday night. While the primary focus remains across southern Wisconsin, a 20-30% chance for precipitation extends into northern Illinois, mainly north of I-80. By Sunday, expect a return to more humid conditions with highs reaching the upper 80s to near 90.

The warm and humid airmass persists through next week. Forecast confidence in daily highs remains moderate, as peak temperatures will depend on convective activity along the northern periphery of a southern states ridge. Periodic waves of showers and thunderstorms are possible near northern Illinois. Should activity remain displaced north into Wisconsin, afternoon temperatures could top out into the low 90s.

KJB

AVIATION /00Z TAFS THROUGH 06Z SATURDAY/

Issued at 615 PM CDT Thu Aug 27 2026

There are no key concerns for the 00Z TAF period.

Easterlies below 10 kt will go light and variable by mid- evening. Expect SW winds largely below 10 kt on Friday. VFR throughout the period.

Doom

LOT WATCHES/WARNINGS/ADVISORIES

IL...None. IN...None. LM...None.