textproduct: Chicago
This forecast discussion was created in the public domain by the National Weather Service. It can be found in its original form here.
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 /18Z TAFS THROUGH 00Z SATURDAY/
Issued at 1222 PM CDT Thu Aug 27 2026
There are no significant concerns through the period.
Winds most of this afternoon will be northeast in the wake of a lake breeze at the near lake terminals and light north-northwest inland. Expect light/VRB to calm winds tonight into Friday morning, becoming light south-southwest by mid morning. A lake breeze will develop by midday Friday, but probably stay east of ORD and MDW.
The calm winds overnight may support BR/BCFG development away from Chicago, and as such, maintained TEMPO MVFR VSBY at DPA, RFD, and DPA. Can't rule out a brief period of IFR, particularly at DPA, especially if skies clear out enough. Spotty sprinkles are possible inland of the lake breeze this afternoon and then overnight/early Friday near and southeast of the Chicago metro.
Castro
LOT WATCHES/WARNINGS/ADVISORIES
IL...None. IN...None. LM...None.
IMPORTANT This is an independent project and has no affiliation with the National Weather Service or any other agency. Do not rely on this website for emergency or critical information: please visit weather.gov for the most accurate and up-to-date information available.
textproduct.us is built and maintained by Joshua Thayer.