Corn Sweat Is Real, And It’s Making The Heat Dome More Miserable

As if wilting humidity from a stubborn high pressure “heat dome” weren’t enough to make about 90 million Americans already feel as if they’re swimming in a thick pool of oppression, the corn is sweating, causing dew points to rise to tropical levels.

“Corn sweat” is no rural legend. More properly, it’s known as evapotranspiration.

Corn’s contributions to humidity are highest around the time of tasseling and pollination, when the flower emerges from the corn stalk. This happens around the end of July and early August, and during this time, an acre of corn give off about 3,000 to 4,000 gallons of water vapor each day, according to the U.S. Geological Survey.

This year, this natural phenomenon coincides with a dangerous heat dome stretching through the Mississippi Valley and parts of the Midwest. The National Weather Service forecast temperatures around 100 degrees Fahrenheit, with dangerous heat index values of around 110 to 115 degrees in states such as Missouri, Minnesota, Iowa, Indiana, Illinois and the Dakotas.

It’s been raining relentlessly, and that hasn’t helped, Bob Oravec, the lead forecaster at the weather agency’s College Park, Maryland, office told Scientific American.

“Everything is wet, saturated,” he said.

That means that in addition to all the water vapor added by transpiration, moisture is also evaporating from the corn and other plants and the ground itself.

“The Midwest is famous for high dew points from the vegetation,” Oravec said.

So Far Beyond The Dreaded ‘Moist’

All plants sweat.

It’s just that there’s so much corn — about 95.2 million acres of it this year, planted in fields averaging around 725 acres — that going out on days like these is like taking a dip in a hot, thick bowl of corn chowder.

This should give anyone pause: A 725-acre cornfield could sweat out between 2,175,000 and 2,900,000 gallons of water vapor a day during the peak growing season.

And if all the acre of corn in America were sweating at the same time, that could add, are you ready for this, something like 380 billion gallons of water a day to already wet, thick air.

Now, compare that to how much the average person sweats — about 1.5 gallons a day, or 4 gallons a day if they’re athletes.

So, theoretically, the 25,000 people riding across corn sweaty northern Iowa this week in RAGBRAI — the Des Moines Register’s Annual Great Bicycle Ride Across Iowa — are adding another 100,000 gallons of water vapor to the steamy mix.

The word “moist” is close to a profanity on rides like that, and this goes so far beyond that, there’s no delicate word for what it feels like to be out in it.

What Are Sweat-Drenched Folks Saying?

To find out, we turned to the unfiltered voice of the people on Reddit.

“Yep. It’s definitely real, and it’s 1000% miserable,” a lifelong resident of middle Illinois corn country commented on another Subreddit, r/weather, adding that late July and August are “brutal every year.”

“Same,” another Redditor empathized. “I grew up in the middle of a cornfield in a valley with no a/c. I currently work outside 5–6 mornings each week. It’s gonna be rough.”

“I couldn’t live where the dew point gets to 85 on the regular,” someone else said. “I would riot.”

“Reason number 5,213,674,992 why I don’t want to live in the Midwest ever,” another person said.

This year, corn sweat and Canadian wildfire smoke are double-teaming some folks, making the air more oppressive and dangerous to some groups.

“I’m newish to Minnesota, and I’m curious, are you good people just used to this high humidity? It’s miserable outside and combined with the Canadian wildfires it’s making this entire spring and summer the worst!” someone posted on an r/Minnesota thread.

“But yet nobody complains and seems to be perfectly fine with it! So leads me to wonder when is the good weather time in Minnesota? When can I open my windows without getting hit with a wall of humidity and or Canadian wildfire smoke?”

Oh, Minnesotans hate it, alright, others pointed out.

“In Minnesota culture, you can’t openly complain about the weather. You make a witty joke out of it like, ‘Who needs a pool with this weather?’”

What’s Superman Got To Do With It?

Some Redditors seem a little punch drunk, as if the corn sweat is adding white lightning or some other hooch to the mix.

“I knew we should’ve been worried about that new Superman actor,” someone said on an r/climate thread, noting, “His name is David Corenswet, which sounds kinda like corn sweat.”

“I’m glad you explained the joke because that’s pretty funny, actually,” another person responded, illustrating how quickly discussions go off the rails on Reddit.

“You beat me to the punch. I thought of making the comment, too,” someone else said.

“I thought they were talking about the ‘corn sweats’ from eating too much buttered corn on the cob too fast,” another person joked.

“Butter sweat,” someone replied, continuing the free-association down the Alice’s rabbit hole that is Reddit.

No Sewer Gas, Though

Inevitably, the discussion turned to who is suffering the, ahem, moist.

“Except that cities are heat islands,” someone on the r/weather thread said, citing research from Yale and NASA finding that buildings, roads and pavement can act as solar collectors and retain the heat absorbed overnight.

“I’m not saying that isn’t true,” someone said. “But when you’ve got a rural town where the concrete is way spread out and it’s surrounded by fields full of corn for X miles, compared to a small city nearby that still has a ton of green spaces everywhere and hasn’t covered every available inch of road frontage in pavement/concrete, it’s going to feel muggier in the small town, even on a cool day.”

“Yeah, but we don’t get sewer steam in agricultural areas, so you’ve got that,” someone on the r/Michigan Subreddit thread said.

Yes, there is that.

Someone on the r/climate thread even blamed an explosion in the salamander population on the corn sweat.

“The house I rent in western PA has a bunch of century old stone walls and a few good places for moisture retention. So seeing an occasional salamander on the property wasn’t the craziest thing,” the Redditer said. “A few years of growing container corn and tomatoes in large numbers, and I’m nearing a very specific amphibian sanctuary.”

Any Relief In Sight?

That might be a cute story if it didn’t point to bigger concerns.

Heat waves like the current one gripping the nation’s midsection are becoming hotter and happening more frequently than in the past because of the added heat trapped by greenhouse gases in the atmosphere due to human fossil fuel use, according to Scientific American.

The publication cited an analysis by the nonprofit Climate Central that found that human-caused climate change made extreme heat events are at least three times more likely for nearly 160 million people, almost half of the U.S. population.

Short-term weather models show the heat dome may persist over the eastern United States for the next week or two.

“The weather pattern is just kind of stagnant and is stuck,” Oravec told Scientific American. “It looks like it’s going to be a hot few weeks.”

The corn will continue to sweat until harvest, although overall humidity typically rocks back before then.

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