How 'Corn Sweat' Is Turning Up the Heat: The Hidden Factor Intensifying Midwest Heat Waves

Evapotranspiration from crops is making heat and humidity more unbearable across the Corn Belt, experts warn

Natalie C. Frank, Ph.D July 25, 2025

Frapestaartje/flickr [CC BY 2.0]

MIDWEST U.S. - As record-breaking heat continues to grip the heartland and push into the East Coast, residents across the Corn Belt are not just facing triple-digit temperatures. They're also experiencing a lesser-known but powerful phenomenon adding fuel to the fire: corn sweat.

Known in scientific circles as evapotranspiration, this process is nature’s way of helping plants cool themselves by moving water from deep within the soil up through their roots and out through their leaves. Once released, that moisture evaporates into the atmosphere, raising humidity and making an already scorching day feel even hotter.

"The term refers to the amount of moisture, the humidity that the plants take from the soil to cool off," explained Bruno Basso, professor of sustainable agriculture at Michigan State University, in an interview with ABC News.

While all vascular plants perform this process, corn stands out for its sheer efficiency. In the heat of midsummer, one acre of corn can push up to 4,000 gallons of water into the atmosphere each day, according to Basso. And that water doesn’t just disappear. It hangs heavy in the air, thickening the heat and creating what experts describe as a “steam room effect.”

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