As dangerously hot weather is set to blister over Chicago this week, a Midwest-centric term "corn sweat" is making its rounds yet again.

Mid-July to mid-August is when crops in the Midwest release the most water because of the combination of their maturity and peak heat.

Heat and humidity will once again smother the eastern half of the country this week, pushing the heat index to dangerous levels for tens of millions of people. In the Midwest, the humidity will be boosted by a phenomenon called “corn sweat.”