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.

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

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.”