Summer Nights Are Heating Up — And That’s Impacting Crops And Livestock

Aug 08, 2022

Climate experts say summer nights have gotten warmer. One study found the average minimum temperature in the United States has gotten warmer by 2.5 degrees over the last 50 years. For farmers, this means crops and livestock could suffer.

This summer, warm nights hurt Kansas farmers and ranchers. Thousands of cattle were killed in June and the corn crop is doing poorly.

“They didn't successfully pollinate and they didn't even put ears of corn on,” said Chip Redmond, a Kansas State Extension meteorologist.

Since 1970, the average minimum temperature across the United States has gotten warmer by 2.5 degrees, according to a study by Climate Central. Dennis Todey, director of the USDA’s Midwest Climate Hub, said that in the Midwest low temperatures have changed more than high temperatures over the past century.

“The consistent message all across the Midwest in the summertime is that our nights are getting warmer,” he said.

This is largely driven by moisture in the atmosphere. Cloud cover is causing more and faster warming at night than during the day. In the Midwest, much of this moisture comes from the Gulf of Mexico and from “corn sweat” — evapo-transpiration of corn takes moisture out of the soil and puts it into the atmosphere.

Climate Central

This graph shows how the average minimum temperature has increased in the United States over the past 50 years.

Cattle impact

In June, cattle in western Kansas experienced heat stress caused by a rapid change in temperature. The cattle had not yet shed their winter coats and the warm nights did not allow the cows to cool down overnight.

University of Missouri Extension veterinarian and cattle rancher Scott Poock said that cows are most comfortable when temperatures are between 40 and 65 degrees. Anything more will cause the cows to expend energy trying to get cool. They may also lose their appetites or stand longer than they should to increase respiration.

“If they don't eat as much, it's gonna affect their milk production,” he said. “And because they're standing longer, they're gonna have an increased chance of becoming lame.”

Warm nights can also affect reproduction. Too much heat can stress the embryo and can also decrease semen quality in bulls.

“Missouri producers should try to breed cows prior to when it gets really hot, because it gets difficult when it gets so hot, especially when it stays hot during the night,” Poock said.

For dairy ranchers, heat abatement includes using sprinklers and fans to cool down the cows. Warm nights can change the schedule for that.

“That's something that dairymen need to know is sometimes we think, ‘well, it's gonna cool down at night. Maybe I don't run my sprinklers at night,’”he said. “But actually, in Missouri during the summer heat abatement needs to continue right through the night.”

Poock said that for beef ranchers who don’t find it worth it to invest in fans and sprinklers, breeding for short hair is important. Cows with so-called slick coats are better able to tolerate the heat.

Crop impact

Scott Poock

Cattle can be bred for slick coats to help them withstand heat. This cow sheds its longer winter coat for its slick summer coat when it warms up.

Crop impact

High overnight temperatures can also negatively impact crops such as corn, wheat, rice, and barley. Warmer overnight temps increase the crops' respiration, leading to increased water use. Crops may also use carbon that's usually used to develop grain cells, which can mean a lower yield.

For corn, it’s particularly dangerous when warm nights occur during the pollination stage, said Mark Licht, an extension cropping specialist with Iowa State University. Cooling off at night during this stage help produce higher yields, so the timing of those high overnight temperatures makes a difference.

“Ideally what we want is temperatures that are above normal during the vegetative growth period — basically up until about a week before pollination,” he said. “So at pollination or slightly before, we'd really like to see temperatures go below normal.”

Chip Redmond said warmer temperatures hitting Kansas in July was especially bad timing. The conditions were dry and cloud cover led to warm nights during the silking stage.

“It never really gave the crop a chance to breathe, very similar to what happened in June with the cattle, except this time it was really badly timed with corn in Kansas,” he said.

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Video: Why Your Food Future Could be Trapped in a Seed Morgue

In a world of PowerPoint overload, Rex Bernardo stands out. No bullet points. No charts. No jargon. Just stories and photographs. At this year’s National Association for Plant Breeding conference on the Big Island of Hawaii, he stood before a room of peers — all experts in the science of seeds — and did something radical: he showed them images. He told them stories. And he asked them to remember not what they saw, but how they felt.

Bernardo, recipient of the 2025 Lifetime Achievement Award, has spent his career searching for the genetic treasures tucked inside what plant breeders call exotic germplasm — ancient, often wild genetic lines that hold secrets to resilience, taste, and traits we've forgotten to value.

But Bernardo didn’t always think this way.

“I worked in private industry for nearly a decade,” he recalls. “I remember one breeder saying, ‘We’re making new hybrids, but they’re basically the same genetics.’ That stuck with me. Where is the new diversity going to come from?”

For Bernardo, part of the answer lies in the world’s gene banks — vast vaults of seed samples collected from every corner of the globe. Yet, he says, many of these vaults have quietly become “seed morgues.” “Something goes in, but it never comes out,” he explains. “We need to start treating these collections like living investments, not museums of dead potential.”

That potential — and the barriers to unlocking it — are deeply personal for Bernardo. He’s wrestled with international policies that prevent access to valuable lines (like North Korean corn) and with the slow, painstaking science of transferring useful traits from wild relatives into elite lines that farmers can actually grow. Sometimes it works. Sometimes it doesn’t. But he’s convinced that success starts not in the lab, but in the way we communicate.

“The fact sheet model isn’t cutting it anymore,” he says. “We hand out a paper about a new variety and think that’s enough. But stories? Plants you can see and touch? That’s what stays with people.”

Bernardo practices what he preaches. At the University of Minnesota, he helped launch a student-led breeding program that’s working to adapt leafy African vegetables for the Twin Cities’ African diaspora. The goal? Culturally relevant crops that mature in Minnesota’s shorter growing season — and can be regrown year after year.

“That’s real impact,” he says. “Helping people grow food that’s meaningful to them, not just what's commercially viable.”

He’s also brewed plant breeding into something more relatable — literally. Coffee and beer have become unexpected tools in his mission to make science accessible. His undergraduate course on coffee, for instance, connects the dots between genetics, geography, and culture. “Everyone drinks coffee,” he says. “It’s a conversation starter. It’s a gateway into plant science.”