textproduct: Chicago

KEY MESSAGES

- Hazardous swimming and boating conditions will persist at southern Lake Michigan beaches through tonight.

- Heat, humidity, and chances for storms will return early next week.

DISCUSSION

Issued at 215 PM CDT Wed Jul 22 2026

Regional surface observations and GOES visible satellite imagery depict atmospheric conditions this afternoon that are more typical for September or early October rather than July with fairly expansive, broken stratocumulus coverage noted across the Upper Midwest amidst surface temperatures in the mid 60s to mid 70s. The intrusion of this early fall-like air mass yielded brisk northerly winds over Lake Michigan that helped whip up some choppy waves across the lake's southern shores. These high waves -- along with an associated elevated risk for rip currents -- persist at southern Lake Michigan beaches at this hour, but should continue to gradually subside into tonight as the center of a ~1022 mb surface high slides closer to the area.

Dry weather with comfortable humidity levels will continue into tomorrow as the surface high positions itself over the southern Great Lakes. Tomorrow's high temperatures will be a few degrees higher than today's highs, and temperatures will warm further on Friday and into the weekend as the present air mass is prodded eastward by a building mid- to upper-level ridge across the central third of the country. An upper-level shortwave will also drift southeastward across the Lower Midwest on Friday and will be accompanied by rain. According to the majority of the latest forecast guidance, the lingering influence of the aforementioned high pressure should tend to keep this rain suppressed off to our southwest and south. Have thus maintained a dry forecast for Friday, but couldn't rule out needing to introduce mentionable PoP chances for our southern counties at some point if guidance as a whole trends a little farther to the north/northeast with this precipitation.

By early next week, decidedly more July-like conditions will be in place across the region once again with temperatures building into the upper 80s and 90s. Dew points are also expected to climb into the 70s (and possibly well into the 70s) as rich Gulf moisture drifts into the region and is enhanced by evapotranspirational processes occurring across cropland. Heat indices will thus at least approach, and could potentially exceed, the 100 degree mark on Sunday and again on Monday. In addition, this juicy air mass will likely support episodic thunderstorm chances across the region while it is in place. The elevated levels of moisture and instability that will be present across the region during this time frame will likely support threats for severe thunderstorms and flash flooding somewhere in the Midwest as well, though only time will tell precisely where and when such threats may materialize early next week.

Ogorek

AVIATION /00Z TAFS THROUGH 06Z FRIDAY/

Issued at 630 PM CDT Wed Jul 22 2026

Northeast winds will become light and variable this evening as surface high pressure expands across the region. A weak lake breeze is expected to turn winds easterly Thursday afternoon near the lake. Have maintained an early afternoon timing at ORD/MDW for now though confidence in timing and how far inland it reaches remains low. Winds then become light and variable again with sunset. SCT to BKN VFR cumulus can be expected again on Thursday with increasing high clouds expected toward the end of the period.

Petr

LOT WATCHES/WARNINGS/ADVISORIES

IL...Beach Hazards Statement until 10 PM CDT this evening for ILZ006-ILZ103-ILZ104.

IN...Beach Hazards Statement through Thursday morning for INZ001- INZ002.

LM...Small Craft Advisory until 10 PM CDT this evening for the IL nearshore waters.

Small Craft Advisory until 4 AM CDT Thursday for the IN nearshore waters.