This story is made possible through a partnership between Flatwater Free Press and Grist, a nonprofit environmental media organization.

When Emily Elowsky’s air conditioner went out on a hot July day, the heat and humidity in her house felt oppressive.

After putting up blackout curtains and taking a cold shower, she hoped the nighttime temperatures would bring some relief. By 11:30 p.m., though, the house was around a suffocating 82 degrees.

“I tried to just tough it out,” Elowsky said. “I was like, ‘Well, if I just fall asleep, it’ll be fine.”

Extreme heat waves and 100-degree days often get the attention in climate change. But Nebraska’s minimum temperatures also have shot up, presenting an often unseen, overnight threat to people, livestock and crops.

This July, the average minimum temperature in Nebraska – 64.6 degrees – was tied for the state’s eighth-warmest over the past 131 years, according to the National Oceanic and Atmospheric Administration. That’s 3.7 degrees above the average from the previous century.

While Nebraska’s maximum temperatures were around average this past August, the state’s minimum temperatures were much above average, said Eric Hunt, a University of Nebraska-Lincoln agriculture meteorology and climate resilience extension educator.

The trend has implications for Nebraska’s climate. In the coming decades, Nebraska’s minimum temps could be in the low 70s – more akin to southeast Kansas and southern Missouri, Hunt said.

And it threatens the critical reprieve that the human body needs from a cooler nighttime.

Heat can stress the cardiovascular system, kidneys, respiratory system and mental health, said Jesse Bell, director of the University of Nebraska Medical Center’s water, climate and health program.

“All these systems in our body are being impacted every time we experience extreme heat events. … It’s not just the extreme on the high end, but it’s also the minimum temperatures as well,” Bell said.

Rising nighttime temperatures could also threaten Nebraska’s ag interests – both corn and livestock require optimal minimum temperatures to cool down.

Hidden Danger

During the recent early September heat wave, when temps hit the mid-90s and lows stayed in the 70s, Pat Wilson-Johnson came to the Salvation Army’s North Corps Community Center for lunch.

The location functions as a cooling center during high heat days. Scott Harris, who works at the center, said many people will have lunch and then sit in the lobby to cool off and drink water. The location also gives out bags of ice for people to stay cool when they leave.

From growing up in Omaha, Wilson-Johnson remembers cool summer nights when she could let in the breeze from an open window. Now, she said, that just lets in the humidity.

“Nine o’clock at night, it’s still 90, 91 degrees. That’s not right,” Wilson-Johnson said.

The Siena Francis House operates another cooling center during heat advisories. While they’re typically open from 11 a.m. to 4 p.m., Kristy McKern, director of case management and permanent supportive housing, said the organization has staff and protocols in case people need resources outside of these times.

In Lincoln, the Lincoln-Lancaster County Health Department created an extreme heat response plan over a year ago. While the department has focused on high daytime temperatures, they are beginning to look at nighttime temperature data, a department spokesperson said.

Right now, the Lincoln area has one cooling center that operates overnight.

Hunt pointed to the historic 1995 Chicago heat wave – in which over 500 people died – to illustrate the risks from high minimum temperatures.

“That was actually a pretty high mortality event, and the air temperatures over there were insanely high,” Hunt said. “But it probably really was the minimum temperatures staying in the 80s overnight for two, three days in a row that really was actually what killed people, because … no one ever got a chance to cool off.”

These high minimum temperatures don’t affect everyone equally. People more at risk include the elderly and those with certain health conditions and on certain medications. It’s also more dangerous for people who have to function in the heat: those without working air conditioning, people who are homeless, student athletes and people who work outside.

“We have to make sure that we’re addressing extreme heat impacts now, since we’re in a changed climate, so that we are better adapted to the impacts that they’re going to face into the future,” Bell said. “A lack of planning and preparedness is what causes the adverse human health outcomes of these types of events.”

Siena Francis and its partners travel throughout Omaha during high heat days, providing water, snacks and sunscreen to folks who are staying outside. The organization works with some people who have mental illnesses and substance abuse problems.

“A lot of these people don’t have access to just the essentials like you and I would have,” McKern said. “So again, for us to be able to provide those things to them, so they don’t end up in the hospital or they don’t end up dehydrated or passing out or fainting.”

Bell said that on average in the United States, more people die from heat-related deaths than any other weather event.

And it matters even when it’s not deadly. High heat at night also makes it difficult to sleep. According to a report organized by Climate Central, residents in Omaha and Lincoln are estimated to have lost about 30 hours of sleep annually between 2020 and 2025 due to heat, and three of those hours are attributed to climate change.

For those with air conditioning, the heat continuing into the night can mean higher energy bills. Residents living in low income housing or older homes and buildings that haven’t been weatherized could be more susceptible.

Elowsky’s August electricity bill was more than double what she paid in April.

“There’s a lot of homes that are as old as mine … if they haven’t had their windows redone. … I mean, they’re basically sieves for this heat and for the cold,” Elowsky said.

This summer, Steph Earhart blacked out windows to control the apartment’s temperature and save on electricity. Even with the air conditioning on and a fan blowing, Earhart has woken up multiple nights sweating.

The stress of the nighttime heat came to a head when Earhart’s air conditioner went out in the middle of the night during a July weekend as the Lincoln resident was taking care of four pet ferrets.

When the thermostat hit 80 degrees at 2 a.m., Earhart drove to their family’s house in a panic, worried the ferrets would overheat. 

“I am hot, exhausted, and now far away from the place I’m able to control my life,” Earhart said. “It hit me that I had to basically upend everything in my life because my apartment that I had created so I could exist in had become unlivable.”

New Livestock Reality

The rising nighttime temperatures also pose a concern for livestock in eastern and central Nebraska where humidity is rising.

The combination of the two prevents animals from sweating and cooling off effectively, said Rick Stowell, a UNL professor and animal environment extension specialist. Western Nebraska also has seen a rise in nighttime temperatures and humidity, but it is starting from a lower baseline.

Livestock, including cattle, pigs and chickens, make up a number of Nebraska’s leading commodities.

Cooling off at night can be essential for livestock that typically offload the heat they experience during the day.

“The effects of heat stress overall tend to affect larger, more productive animals the most,” Stowell said. “So, if you think about heavy animals, mature animals, fat cattle and a sow, for example, or a high-producing dairy cow, they are generating a lot more body heat, and so they have a lot more heat to get rid of.”

Some heat-stressed animals, like a finishing pig, a steer in a feed lot or a broiler chicken, will typically stop eating and stop putting on weight, Stowell said. A dairy cow’s milk production might drop. A pregnant animal, like a sow or cow, could lose the pregnancy.

Worst case, producers with feedlots could have animals die. The risk grows as the animals gain weight and are nearly ready to go to market, Stowell said. The loss to the farmer is higher then because of the money they have invested.

“Most livestock producers and poultry producers (in eastern Nebraska) are well aware that the situation is getting more challenging,” Stowell said.

To adapt, producers are building more shade structures in feedlots, something Stowell has seen more of over the last 20 years. Other strategies: increased ventilation in buildings, altered feeding schedules and sprinkling water on the ground and in feedlots for cooling. 

“I don’t think there’s any question that every industry in the livestock industry sector in the Midwest would say that heat challenges, summer conditions are … a significant issue that we’re going to have to deal (with) more and more in the future,” Stowell said. 

Crop Yields

Nebraska’s two leading crops also can be harmed – which in turn would harm a farmer’s bottom line – when nighttime temperatures stay high.

Those nighttime higher temps mean that corn and soybeans use more energy instead of storing it. That can impact growth, said Tom Hoegemeyer, a retired UNL professor of practice specializing in agronomy and horticulture, and George Graef, a UNL agronomy and horticulture professor focused on soybean breeding and genetics.

Depending on the timing, duration and intensity of these temperatures, the higher nighttime temps could result in smaller and fewer seeds and biomass for soybeans, Graef said.

And if there are multiple warm days and nights, corn crops begin “shutting down and losing a week or more of filling time in late summer and early fall that we would normally get, which pretty significantly impacts yield,” Hoegemeyer said.

Nighttime temperatures over 70 degrees are likely detrimental for corn crops, Hoegemeyer said. Soybean yields begin to see negative impacts when nighttime temperatures are around 73 degrees, Graef said. The more nights with high nighttime temperatures, the more both crops are impacted. 

In the short term, there is concern that these higher nighttime temps combined with drought could mean increased usage of groundwater in irrigated production, Hoegemeyer said.

Fungi and bacteria could also hurt corn crops when it’s hot and humid at night, which means more chemicals could be sprayed on the crop to protect them, Hoegemeyer said. 

Given these nighttime temperatures, Graef said the soybean industry is employing new technology and capabilities to evaluate and adapt the crop to the changing conditions. He’s confident new variants will be identified.

While the corn industry has been aware of this issue for the last 30 years and has been able to adapt corn crops to better tolerate these conditions, Hoegemeyer is worried how effective this will be long term.

“If you believe the projections as to what temperatures will be like, say, by 2100, we may not be able to do that,” Hoegemeyer said. “There are limits to what we can do with genetics and technology.”

This story was originally published by Flatwater Free Press, an independent, nonprofit newsroom focused on investigations and feature stories in Nebraska that matter. Read the article at: https://flatwaterfreepress.org/rising-temperatures-present-an-overnight-threat-too/