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Is Corn Sweat to Blame for the Heat Wave?

By   /  July 25, 2016  /  1 Comment

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If you saw CNN’s news ticker last week and read that corn sweat is to blame for the heat dome, and your response was “WHAAT??!” you were right to be skeptical. Here’s the Scoop.

First, No, corn sweat did not cause the heat wave. The heat wave was caused by a massive dome of high pressure centered over North America’s mid-section. But it could make things feel hotter.

“Corn sweat” is simply evapotranspiration, or how moisture in plant leaves evaporates into the air. A plant draws water out of the ground, and that water is exposed to the air once it gets into the leaves above ground. Then it evaporates just like sweat does off our skin, though it doesn’t help to keep the plant cool.

All this evaporation from leaves can make things more humid.  And humidity tends to make temperatures feel hotter than they are.  So if you’re surrounded by huge fields of corn, or any other large quantity of leafy green vegetation, humidity might be higher, and so it will feel even hotter than it really is. You can use the heat index table to figure out how hot it feels to your body when you combine temperature and humidity.

Heat Index Table

To see if corn sweat is affecting you, here’s a map of where most of the corn is grown in the U.S.

Where Corn Grows

Now here’s a map showing the heat index, or how hot it felt on July 20, 2016 thanks to the heat dome and humidity. Some of the high temperatures are shown over areas where there’s a good deal of corn, but there are hot temperatures where there is no corn. So it’s hard to get a correlation from these pictures.

map_specnewsdct-08_ltst_4namus_enus_650x366

What I can tell you, living down here in Tucson where there is no corn and pretty low humidity, even a dry heat is hot when it starts to go over 100. So, no matter where you live and how close you are to corn, be careful out there. Choose shade and drink lots of water!

Thanks for reading!

Kathy and Rachel

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  • Published: 4 months ago on July 25, 2016
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  • Last Modified: July 25, 2016 @ 11:41 am
  • Filed Under: The Scoop

About the author

editor and contributor

Kathy worked with the Bureau of Land Management for 12 years before founding Livestock for Landscapes in 2004. Her twelve years at the agency allowed her to pursue her goal of helping communities find ways to live profitably AND sustainably in their environment. She has been researching and working with livestock as a land management tool for over a decade. When she's not helping farmers, ranchers and land managers on-site, she writes articles, and books, and edits videos to help others turn their livestock into landscape managers.

1 Comment

  1. Kathy Voth says:

    Richard Sparks of the NRCS sent me this really great note on this topic. Here you go:

    “A plant draws water out of the ground, and that water is exposed to the air once it gets into the leaves above ground. Then it evaporates just like sweat does off our skin, though it doesn’t help to keep the plant cool.”

    This statement is probably incorrect. During the loss of water from ET, it changes from a liquid to a vapor does involve a lot of cooling for plants. Without ET, the temperature of the leaves from solar energy would increase to the point the plant would die. In fact cooling is a major role of water in the plants, along with providing oxygen for photosynthesis. It doesn’t cause heat, it absorbs heat and increases humidity of the air surrounding the plant.

    Thanks to Richard for adding important info to this!!

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