Temperatures head toward 94° in Chicago Wednesday. It’s only the third time since 1970 the three opening days of August have each posted a 90° high.
Thunder is to rumble over sections of the area Wednesday afternoon and evening. Early indications are the storms may affect 40 to 60% of the Chicago metro area on what promises to be the hottest and most humid day of the current hot spell. With nearly 2” evaporated water in the air above Chicago, any thunderstorms Wednesday could be prolific rain producers where they occur because they are likely to be slow movers.
Dry soils limited atmospheric moisture levels Tuesday--as reflected by low 60° dewpoints at the time of Tuesday’s afternoon 92° high. Dewpoints in the low 60s produce a moderately humid feel—but are well below the truly muggy, oppressive feeling 70°+ dewpoints which dominate the Gulf Coast region.
The result was a peak heat index of just 93° Tuesday.

Hot weather continues Tuesday. A 25th day of 90° temperatures is predicted at Midway Airport. That’s more than six times all of last year’s 90s at the site (there were only four of them). It’s also the most 90s to occur in Chicago by August 2 since the 31 at this point in the infamous Summer of 1988—a year which included a drought responsible for devastating crops across the nation’s heartland.
Hot as this August’s opening days are, the readings pale in comparison to the highs and lows recorded during the month’s opening four days in 1988—100°/78°, 100°/79°, 95°/79° and 97°/78° respectively.
Tucson, Arizona just finished its hottest July ever—and the city’s hottest single month on the books since 1895. Not only did the city endure 39 consecutive 100°+ days—a string of hot days which began in June—but July closed with an average temperature of 90.6°