Much of the central U.S. is bracing for the worst heat wave since 2013:
Temperatures [in Chicago] Thursday are expected to reach 34°C and 37°C on Friday, with humidity levels creating a heat index that feels more like 38-42°C, according to Kevin Donofrio, meteorologist with the National Weather Service.
The heat wave will continue through the weekend, with temperatures only a few digits lower during the day Saturday and Sunday and remaining around 25°C and even 28-29°C overnight, Donofrio said. Temperatures are expected to drop early next week.
It's already starting. I'm heading to Wrigley Field in a couple of hours, and the temperature has already hit 30°C at O'Hare with a heat index of 31.6°C.
WGN has an informative graphic explaining why this is happening.