The combination of corn sweat, the exhalation of water vapor through leaves, and a heat dome is bringing dangerously hot conditions to millions of people.

The heat wave baking the central United States this week may feel worse than those earlier in the summer, and corn is partly to blame, forecasters say.

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.