Can’t Cool Down This Summer? Corn Might Be To Blame

If you’re north of the Mason-Dixon line and have been feeling a little sweatier than usual, you’re not alone. The Midwestern and Northeastern regions are just coming out of an extreme surge of heat and humidity. In fact, he week of June 21 saw a record-breaking wave of humidity across nearly 40 states, with an oppressive humidity level that felt “like a tropical rainforest,” according to data from The Washington Post and global weather forecasting model ECMWF. So where is all this humidity coming from exactly?

Evaporation from rainfall, waterways, and soil adds water vapor to the air, raising absolute humidity levels. But the process of transpiration—water evaporating from inside a plant—also contributes to an increase in humidity levels. One of the biggest agricultural culprits of transpiration? Corn. And this is why you’ve probably been hearing the term “corn sweat” a lot lately.

What Is Corn Sweat?

Corn sweat is a colloquial name for corn plant transpiration—when corn releases water vapor into the air through pores in its leaves. In a way, the corn is actually sweating. Just like humans, the plant moves water from inside its structure to the outside to cool itself down.

In regions where a lot of corn is grown, like the Midwest’s “corn belt” (which includes portions of most Midwestern states), the amount of corn grown can actually have an impact on humidity levels. And while corn sweat will never be the only contributing factor to a sweltering humid day, it does move the needle—sometimes significantly.

According to the USDAover 95 million acres of corn were planted in the States this year. One acre of corn can lead to 3,000 to 4,000 gallons of water vapor in the air each day, according to the U.S. Geological Survey. That’s a lot of corn sweat.

We asked an expert corn farmer for even more context. “There is a definite effect of the ‘feels like’ temperature in a cornfield during the hottest part of the day,” explains Rob Shenot, owner of Shenot Farm.

But why corn specifically? He continues by adding that how the summer favorite is planted could be a factor. “When you compare corn to crops like cucumbers or peppers, corn is planted at a much higher density per acre and also grows much taller, trapping heat and moisture. The taller it is, the greater the effect.” Though he notes, “Once the corn is at full maturity, the transpiration rate certainly drops.”

Shenot personally combats these effects by harvesting sweet corn early in the morning. “The sugar content in the ear is much higher at that time when temperatures are cooler. In the heat of the day, the sugar gets drawn into the stalk. We also harvest in the a.m. for our own comfort. If you find yourself still picking at 11 a.m., things can start getting kind of miserable.”

Late July to early August is the peak growing season, so corn is adding to the humidity now more than ever. While Shenot adds that Western Pennsylvania, where his farm is located, likely doesn’t see any significant weather differences from corn “since most growers are sporadically located,” he adds, “In the case of the Midwest, where corn can be measured in square miles instead of acres, maybe you can feel that a little more.”

What To Know About the Effects of Corn Sweat

According to Science.org“more humidity makes it harder for the body to maintain a safe core temperature and ward off heat stroke.” So if you’re having a harder time cooling down, you can blame the humidity—and the corn sweat. The closer you are to corn crops, the more severe the humidity. (Sorry to all you Iowans out there!)

When the temperature and humidity rise, make sure to follow ready.gov’s best practices for staying safe before, after, and during an extreme heat wave. And check out our array of no-cook recipes so you don’t have to unnecessarily heat up the kitchen.