Monday, September 26, 2022
HomeNotes From KathyIs Corn Sweat to Blame for the Heat Wave?

Is Corn Sweat to Blame for the Heat Wave?

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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Kathy Voth
Kathy Vothhttps://onpasture.com
I am the founder, editor and publisher of On Pasture, now retired. My career spanned 40 years of finding creative solutions to problems, and sharing ideas with people that encouraged them to work together and try new things. From figuring out how to teach livestock to eat weeds, to teaching range management to high schoolers, outdoor ed graduation camping trips with fifty 6th graders at a time, building firebreaks with a 130-goat herd, developing the signs and interpretation for the Storm King Fourteen Memorial trail, receiving the Conservation Service Award for my work building the 150-mile mountain bike trail from Grand Junction, Colorado to Moab, Utah...well, the list is long so I'll stop with, I've had a great time and I'm very grateful.

1 COMMENT

  1. 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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