Wednesday forecast: Dangerous heat wave arrives with abundant sunshine

Chicagoland is about to feel its hottest stretch of 2025 so far.

Wednesday begins with a mix of sun and clouds but skies will trend sunnier as the day proceeds with only a scattering of puffy fair weather cumulus clouds expected.

Intense heat and humidity will push the heat index to a sweltering 105 to 110 degrees, making it dangerously hot for prolonged outdoor activity.

Temperatures will peak near 96 degrees, with southerly winds between eight to 18 mph, gusty at times.

By Wednesday night, skies remain mostly clear, but it will stay warm and humid. Overnight lows won’t offer much relief, bottoming out around 80 degrees.

Stay cool, hydrate often and check on vulnerable neighbors as this brutal heat wave settles in.

Heat Advisory

A Heat Advisory goes into effect beginning at 10 a.m. on Wednesday and runs through 10 p.m. on Thursday night for the entire area.

Beach forecast

Area beaches are expected to be heavily populated with many area residents looking for ways to beat the heat. A modest 1-2 foot chop on Lake Michigan is expected with refreshing 70-74 degree Lake Michigan water temperatures. 

Sunburn forecast

Strong sun and high temperatures will allow unprotected individuals to get a sunburn in only 18 minutes at peak time of 1 p.m. and 45 minutes at 4 p.m.

Wednesday highs across the United States

An estimated 42% of the contiguous U.S. will experience 90-degrees or warmer temperatures on Wednesday afternoon.  

Wednesday departures from normal

Highs are forecast to be double digits above normal over a large swath of the Great Lakes, including the Chicagoland area. 

Wednesday heat risk

More than 38 million U.S. residents are expected to experience major to extreme heat risk.    

The intense heat peaks on Thursday across the Chicagoland area with highs soaring into the upper 90s, the hottest temperatures in about 11 months across the Chicagoland area, since the mercury hit 99-degrees on August 27, 2024.  

The intensity of the heat backs off a bit after Thursday, but highs are still expected to be quite warm, topping out in the lower 90s, with a heat index in the middle to upper 90s. 

Thursday departures from normal

Highs well above normal expected from the Great Lakes eastward into the Ohio Valley and Northeast.   

Thursday heat risk

More than 68 million U.S. residents are expected to see a major to extreme heat risk. 

Thursday severe outlook

As a cold front approaches from the west, scattered thunderstorms will be possible, especially late Thursday night into Friday morning. Currently, the metro area is in a level 1 of 5 or Marginal Risk of seeing a strong or severe thunderstorm.  

Forecast average temperature anomaly July 22 through 28

Strong cooling out west while much above normal temperatures dominate from the Midwest to the Eastern U.S. 

Forecast average temperature anomaly July 29 through August 4

Hot pattern breaks down into early August across the Great Lakes and Northeast as upper steering winds shift northwest out of Canada. 

Key NWS messages about upcoming heat wave