Dangerous temperatures will persist across parts of the U.S. through July, and in some areas, there's an unexpected contributor.

It is “corn sweat” season. The biggest U.S. crop does influence our weather here in Michigan and across the Midwest. All plants drink up moisture from the soil and then breathe some of it out in a process called transpiration. The transpiration puts water vapor in the air and increases the humidity.

Corn sweat is an agricultural phenomenon that makes humidity during a heat wave even worse, especially in states like Illinois where it's a major cash crop.