textproduct: Chicago

KEY MESSAGES

- Generally above normal temperatures (highs in the 80s) and dry conditions are expected through early next week. Onshore winds will keep temperatures cooler near Lake Michigan each day (60s-70s).

- Backdoor cold fronts will lead to cooler conditions (60s and 70s) extending farther inland late Wednesday into Thursday and potentially again over the weekend.

DISCUSSION

Issued at 217 PM CDT Tue May 26 2026

A mid-level ridge axis continues to reside across the southern Great Lakes which is maintaining generally tranquil weather conditions. Despite the widespread cirrus coverage overhead, temperatures continue to warm into the lower to mid-80s which is just about at their peak for today. That said, a lake breeze is developing near the lake and will begin to ooze inland over the next few hours resulting in locally cooler temperatures near the lake.

Heading into tonight, the ridge axis will begin to move east of the area as the broad trough over Ontario digs into the northern Great Lakes. At the same time, the low center over southwest IL and eastern MO will continue to lift towards the area tonight. Associated with this low are some scattered showers and a few thunderstorms, but their coverage should weaken as the low approaches due to the drier air across northern and northeast IL and northwest IN. However, there is still a 15-20% chance for an isolated shower or two to brush our southern CWA (namely areas along and south of US-24) overnight. Otherwise, dry conditions can be expected with light and variable winds and mild temperatures in the lower to mid-60s.

By Wednesday the aforementioned surface low will begin to drift east across central IL and IN as a cold front begins to race southward out of WI and northern Lake Michigan. While a few showers (and perhaps and isolated rumble of thunder) may linger along/south of US-24, mostly dry conditions are expected across the rest of the area. The cold front is expected to move through northern IL and northwest IN late Wednesday afternoon and evening which will result in quickly cooling temperatures in its wake, especially near the lake. Given the late arrival of fropa, highs on Wednesday look to still be able to reach into the lower to possibly middle 80s inland but prevailing onshore winds will keep lakeside temperatures notably cooler in the 60s to around 70. However, if the front arrives faster than forecast then highs could end up being a few degrees cooler areawide. Regardless, the frontal passage looks to be mostly dry though there is still a 15-20% chance for an isolated shower or thunderstorm to develop near the IL-WI line.

In addition to the cooling temperatures, the front will also bring breezy north-northeast winds to the area with gusts upwards of 20-25 mph Wednesday evening through Thursday. With the onshore wind direction the winds will also result in building waves and an increased risk for rip currents on Lake Michigan. Therefore, dangerous swimming conditions are forecast Wednesday night through Thursday.

High pressure is expected to build back into the Great Lakes Wednesday night through weeks end which will result in dry and tranquil weather conditions. Though, persistent northeast winds do look to keep temperatures more in the seasonable range with daily highs in the upper 70s to lower 80s (60s near the lake), especially on Thursday, and overnight lows in the 50s through next weekend.

Yack

AVIATION /00Z TAFS THROUGH 06Z THURSDAY/

Issued at 626 PM CDT Tue May 26 2026

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

SE winds below 10 kt this evening will go light and variable tonight. Winds will establish a NE direction by mid-morning Wednesday moving at less than 10 kt through the afternoon, and closer to 10 kt during the evening. Expect VFR throughout the period.

Doom

LOT WATCHES/WARNINGS/ADVISORIES

IL...Air Quality Alert until 6 AM CDT Thursday for ILZ005-ILZ006- ILZ012-ILZ013-ILZ020-ILZ021-ILZ103-ILZ104-ILZ105-ILZ106- ILZ107-ILZ108.

Beach Hazards Statement from Wednesday evening through late Thursday night for ILZ006-ILZ103-ILZ104.

IN...Air Quality Alert from midnight tonight to midnight CDT Wednesday night for INZ001-INZ002-INZ010-INZ011.

Beach Hazards Statement from late Wednesday night through late Thursday night for INZ001-INZ002.

LM...Small Craft Advisory from 10 PM Wednesday to 10 PM CDT Thursday for the IL nearshore waters.

Small Craft Advisory from 4 AM Thursday to 1 AM CDT Friday for the IN nearshore waters.