Corn sweat, a Midwestern phenomenon, could increase humidity levels in already-sweltering states—from Ohio to Illinois—through Thursday.

In Iowa, corn pumps out "a staggering 49 to 56 billion gallons of water into the atmosphere each day" throughout the state, the National Weather Service said. That can add 5 to 10 degrees to the dew point, a measure of the humidity in the air, on a hot summer day.

Another heat wave is expected in Wisconsin this week. Here's how a scientific process nicknamed "corn sweat" could be making it feel hotter.