Summer nights in the South are getting hotter, quicker

Hotter overnight temperatures mean less ‘cooling off’ time for people, increasing risks for heat-related illness

Nighttime temperatures have risen faster than daytime temperatures across the Southeast during the region’s warmest decade on record, creating unrelenting heat waves that can have serious consequences for vulnerable people, farm animals and crops — including death.

For Atlanta and other cities, the misery is compounded by high humidity, which boosts heat indices, and the urban heat island effect, in which pavement and buildings generate and trap heat, making cities significantly warmer than rural areas.

In July, Atlanta’s average minimum temperature, or overnight low, was a torrid 73.5 degrees, a full 4.6 degrees higher than the 20th century average. The contiguous U.S. overnight low was 63.6 degrees, 3 degrees above average for the month, making it the warmest July on record for nighttime temperatures.

While anyone can be at risk for heat-related illness, some are more vulnerable, including older adults, those who are pregnant, those with heart or lung conditions, young children, athletes and outdoor workers, said Claudia Brown, a scientist with the Climate and Health Program of the Centers for Disease Control and Prevention.

“An increase in summer night temperatures means less ‘cooling off’ occurs, and if the body does not cool sufficiently after a hot day, you may be more at risk of heat-related illness and death,” Brown wrote in an email.

Heat-related health effects may include death from heat stroke, or cardiovascular and respiratory complications, renal failure, electrolyte imbalance, kidney stones, harm to fetal health and preterm birth, she added. Some studies have shown that elevated nighttime temperatures contribute significantly to heat-related mortality, particularly when hot nights follow hot days.

Prolonged heat waves are particularly hard on those without shelter, as well as those who lack air conditioning or who struggle to afford cooling costs.

Willie Pierce, 73, a retired Braves groundskeeper, has lived in an older home in Kirkwood without air conditioning for more than 40 years. During the worst of the sweltering summer, Pierce usually spends his days outside his house and at night, he uses a fan.

Now, however, thanks to a local nonprofit, Neighbor in Need, he’s looking forward to finally getting central air conditioning installed for the first time. The nonprofit, which serves working poor and elderly residents in East Atlanta, arranged donations from licensed contractors and will cover the remaining cost of a system that could easily run over $10,000, including installation.

“I got lucky,” Pierce said. “I can’t afford to get that kind of work done.”

Nationally, low-income households pay a higher percentage of their income on energy, including cooling costs, according to the U.S. Department of Energy. The Southeast, in particular, has some of the starkest disparities between rich and poor when it comes to energy cost burdens.

In Georgia, all households spend an average of 3% of income on energy, according to the Low-Income Energy Affordability Data tool from the U.S. Census (using the most recent federal data from 2018). But the lowest-income households in the state — those making 30% of area median income or less — spend an average of 21% of their income on energy.

Credit: SPECIAL

Credit: SPECIAL

Protip Biswas, vice president of homelessness for United Way of Greater Atlanta, said his organization has seen a steady increase in requests for rent and utility assistance. Although he said there were likely many factors driving the trend, including rising rents, he has heard anecdotally from people who say they are choosing not to run air conditioning because of the cost.

“Increased utility bills are because of a number of reasons, and one of them could be climate,” Biswas said. “This is all connected, and that’s the real factor for lots of low-income people.”

The Georgia Public Service Commission, a body of elected officials who oversee utilities in the state, declined to comment on how it is preparing for a warmer future.

“We are not commenting because we’re a financial not an environmental regulator,” a spokesperson wrote in an email.

Karin Gleason, a climatologist with the National Oceanic and Atmospheric Administration, said the agency’s data corrects for such variables as land-use. That means data from Atlanta in 1930 can be compared with data from 2022 showing real trends not enhanced by urbanization, she said.

It’s not just people in cities who are suffering from hotter nights. Bill Murphey, state climatologist with the Department of Natural Resources, said the higher nighttime temperatures could affect animal and plant ecology such as predator-prey dynamics, plant growth and the nocturnal activities of organisms.

Murphey said the temperature increases across the state over time are consistent with observed changes in climate driven by manmade greenhouse gas emissions. Other potential contributors to the temperature fluctuations are cloud cover, air pollution and urbanization.

“You can look at the trends ... over 50 years, and you can get an idea that yes, we are warming up,” he said. “If you look at July, you can see that.”

Pam Knox, an agriculture climatologist with the University of Georgia College of Agriculture and Environmental Sciences, said Georgia farmers are also being negatively affected.

“If you don’t have that cooling-off period at night, after about three days, you really start to have serious heat impacts,” she said, adding that cattle “don’t want to eat because it’s too hot, and so they don’t gain as much weight, or if they’re dairy cattle, they put out less milk.”

Some crops, such as corn, will also start to fail after too many warm nights, she said.

Knox said farmers will have to adapt by choosing different breeds of cattle, or perhaps investing in shade structures or air-conditioned barns, as temperature and humidity rise.


A note of disclosure

This coverage is supported by a partnership with 1Earth Fund, the Kendeda Fund and Journalism Funding Partners. You can learn more and support our climate reporting by donating at ajc.com/donate/climate/