Air temperatures are expected to rise to dangerously high levels, but it will feel much, much hotter.
Nearly all of the Chicago area will now be under an Excessive Heat Watch for multiple days this week as heat index values could rise as high as 112 degrees for some.
The watch takes effect Thursday afternoon and continues through Saturday evening, with heat indices potentially peaking between 102 and 112 degrees each day.
"The cumulative effects of temperatures and heat index values this high could lead to heat related illnesses with prolonged exposure," the watch states. "Those without air conditioning, elderly, small children, and pets are especially susceptible. Plan ahead."
Here's a look at how hot it is expected to get this week - and how hot it will feel.