By Clarissa Donnelly-DeRoven
From Wilmington to Asheville, a thick heat wave settled over most of North Carolina mid-June, leading temperatures — especially in the southeastern part of the state — to spike into triple digits. Hundred-degree days have appeared yet again this week, with much of the Triangle region under an excessive heat warning. Temperatures are expected to hold steady in the 90s for much of the state through the weekend, leaving those without air conditioning or who work outside with little to rejoice about.
“Heat kills more people than any other weather-related event,” explained Ashley Ward, a policy associate at the Duke Nicholas Institute for Environmental Policy Solutions. Part of the reason heat is so deadly, she said, is because you can’t see it. “When I look out my window today, and it’s going to be 100 degrees outside, it looks exactly the same as when I look out my window and it’s 85 degrees outside.”
Heat’s invisibility means people often have a different risk assessment about it than they do other visible extreme weather events, such as hurricanes or tornadoes, explained Chip Konrad, a climatologist and geography professor at UNC Chapel Hill. People know these are deadly and take their threats seriously.
“But heat?” he said, “When we get heat waves they typically impact multiple states — sometimes the entire eastern U.S. — and any given heat wave is going to impact a lot more people than other weather hazards.”
That wide expanse increases heat’s deadly potential.
“It’s kind of like you’re boiling the frog in the water,” Ward said.
Threat of overheating
Many think the main danger heat waves pose to human health is the risk of dehydration. That’s partially correct, but researchers say that a deadlier risk — an underestimated one — is the way extreme heat prevents the body from being able to cool off.
“One of the symptoms most people cite is a lack of ability to sweat,” Ward said. “What happens is the body’s unable to cool itself through evaporative cooling, which is when sweat on your skin is evaporated into the atmosphere, and then that cools your body temperature down.”
People ultimately die of heat exposure when the body can no longer do this to regulate its temperature. It leads people’s organs — including their hearts — to fail. And while many public information campaigns teach people the ways they can protect themselves from overheating during afternoon highs, researchers say that actually what might be the most dangerous part of the day is overnight.
“The time in which we are most vulnerable to heat illness is when temperatures overnight do not drop below, say, 75 degrees,” Ward said. “Our bodies need time to recover from heat exposure during the day. And when temperatures outside don’t drop below 75, and we return to our homes in which we can’t afford to run air conditioning, or they’re not energy efficient, our body is never able to fully recover. And then the next day we return to that same job, and are exposed again.”
The same is true for days that aren’t exactly part of a heat wave but are still hot.
“When there’s a heat wave or heat advisory or heat warning, workers are really good at reducing their exposure,” said Maggie Sugg, a geography professor at Appalachian State University in Boone. “But they experience the most heat strain and dangerous heat outside of it — in climatologically normal conditions, kind of what we saw at the end of [last] summer.
“We’re really good at behavioral modifications and adaptation when it’s really hot, but just normal North Carolina weather is really warm, right?” she said. “So that seems to be the most dangerous, when people are not quite on guard.”
Exacerbates existing health disparities
All extreme weather events can be thought of as “threat multipliers.”
Researchers across the country have found that heatwaves are more dangerous for people with chronic illnesses, and for elderly people who are socially isolated — meaning they live alone and don’t have friends or family regularly checking on them. Others have documented increases in suicides and pre-term births during high temperatures.
Sugg’s doctoral dissertation examined who in North Carolina was most at risk of ending up in the emergency department for a heat-related illness. She found that people who lived in the southern coastal plains region were the most likely to be admitted to the ER for heat-related illnesses when the temperature spiked — a finding that ran counter to earlier research.
The coastal plains region is rural. Usually, because urban areas are full of concrete and other surfaces which absorb and hold heat, the residents of these regions bear a disproportionate burden of heat illness.
In North Carolina though, the coastal plains regularly see some of the hottest temperatures in the state, many residents work outside in agriculture (compared to urban areas where many work indoors with air conditioning), and it has a high concentration of poor counties — meaning that even if residents have air conditioning, many cannot afford to use it.
In urban areas, community spaces such as libraries or schools can be used as centralized cooling spaces. But in rural areas, people often live farther away from each other and from town centers, making it more difficult for people to actually get to the cooling center, and to communicate to residents that this is an option.
“Heat is like a silent killer,” Sugg said. “It really amplifies existing disparities.”
The role of climate change
While climate change will increase the frequency, duration and strength of heat waves, it will also lead to more hurricanes. This could be yet another ‘threat multiplier’ because late-season heat waves can follow hurricanes. This happened in Louisiana after Hurricane Ida hit in 2021.
“The two can combine in ways that make it a lot worse,” said Konrad, from UNC. After Hurricane Ida, “there were so many people suffering from heat illness because they didn’t have any air conditioning. The temperature was well in the 90s. The humidity was ridiculous.”
Though we’ve seen more heat waves and intense hurricanes in recent years, data from the Centers for Disease Control and Prevention shows that people may be realizing the extent of the threat and taking steps to lessen the impacts.
“Some heat-related illness and deaths have actually decreased in recent decades, or not increased as much as we thought they would,” said Virginia Guidry, who leads the Occupational and Environmental Epidemiology office at the state health department. The decrease could be due to better predictions, educational campaigns or more accessible programs that offer cooling centers or energy payment assistance.
“It’s not as straightforward as we would have thought that when it gets hotter, you start seeing more people in the emergency room,” she said. “Even though that relationship is there, it’s also sometimes attenuated by these actions.”
While heat waves and climate change are systemic issues that require big solutions, there are things individuals can and should do to protect themselves from overheating: stay out of the sun if you can, wipe down your whole body with a cold towel, take a cool shower, sit in front of a fan, and drink plenty of fluids that won’t dehydrate you — that may even mean avoiding a cold beer on a 100-degree day.
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