Dangerous Heat, Humidity Arriving Mid-Week in Chicago With Temps Feeling Like Triple Digits

Patty Wetli | July 21, 2025, 2:47 pm

(Pixabay)

The National Weather Service has issued an extreme heat watch for Chicago on Wednesday and Thursday.

Temperatures are expected to soar between 92 and 97 degrees. High humidity will make it feel more like 105 to 115 degrees, the weather service said.

(National Weather Service Chicago)

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The urban heat island effect will make for a steamy night on Wednesday, with temperatures not likely to fall below 80 degrees, according to Brett Borchardt, senior meteorologist with the National Weather Service Chicago office.

“The No. 1 wild card is thunderstorms,” Borchardt said. “Nothing attracts thunderstorms like heat waves.”

Some forecast models are predicting thunderstorms in the Chicago region Tuesday night into Wednesday, which could delay the onset of the heat wave. “Thunderstorms are nature’s natural air conditioning,” he said.

Likewise, storms are being forecast in the upper Great Lakes and those could push cooler air down Lake Michigan into Chicago, stymieing the heat wave.

On the flip side, if storms don’t materialize, extreme heat could linger into Friday, Borchardt said.

Any relief will be short-lived, with temperatures expected to rebound back into the 90s next week, he said, adding that late July and August are traditionally the hottest time of the year.

“This is likely not the last heat wave of the year,” Borchardt said.

Infants, young children, the elderly, pregnant women and people with chronic illnesses are particularly vulnerable during heat waves, but everyone should take precautions including staying out of the sun, seeking shade and air conditioning, drinking water even when not thirsty, and canceling outdoor events, the weather service advised.

Cooling centers will be open throughout the region.

Note: This article was updated with new information from the National Weather Service.