Corn 'sweat' plays role in heatwave

The dog days of summer are here. Air conditioners are blaring, community pools are filling up and the phrase 'heat index' is getting thrown around on weather broadcasts.

But not many weather experts are talking about corn's influence on the heatwave.

Heat index is a measure of how hot it feels after the humidity, or moisture in the air, is figured in. Moisture in the Midwest can usually be tracked back to the Gulf of Mexico, but this time of year there is added moisture in the air, and it comes from sweating corn, experts say.

Corn sweat, or evapotranspiration, is part of the reason the air feels so muggy in July and August.

Corn, like all plants, gives off water vapor when it takes in carbon dioxide. It sounds pretty harmless when you are talking about a few plants, but the United States Department of Agriculture says that more than 90 million acres of corn is growing in the country's corn belt, which includes Wisconsin.

'An acre of full-grown corn can release up to 4,000 gallons of water into the air on a sunny day,' said Justin Schultz of the National Weather Service.

'It's hard to quantify just how much of an increase to the humidity evapotranspiration causes,' Schultz said. A National Weather Service heat index graph shows that an additional 15 percent of moisture can raise the heat index 24 degrees, causing 100 degrees to feel like 124 degrees.

How does this affect you? Your body sweats when it overheats. As the sweat evaporates off your skin, you experience a cool sensation.

But the more moisture in the air, the slower your sweat will evaporate, which decreases the ability of the body to cool. This can lead to maladies like heatstroke.

Though corn may not be the cause of the heatwave, the crop plays a role in how the heat makes you feel.

Doug Raflik can be reached at draflik@gannett.com