Extreme heat is the deadliest weather-related event in the United States, killing more people than tornadoes or hurricanes – combined.
While federal agencies report about 700 Americans die each year from extreme heat, some studies estimate that figure could be closer to 1,300 deaths per year. Another study found up to 20,000 deaths may have been linked to extreme heat between 2008 and 2017.
Part of what makes a heat wave so dangerous is lack of awareness, experts say. The consequences of extreme heat aren’t as visually obvious as other natural disasters, but they can be especially life-threatening to certain people depending on how old they are, what medical conditions they have and where they live.
“When a heatwave rolls in, people don’t usually connect it to the injuries and loss of life that occurs,” said Shawn Gibbs, dean of Texas A&M University School of Public Health. “We tend to underestimate it.”
How extreme heat impacts your health
Extreme heat causes cellular dysfunction, preventing cells from working properly, health experts say.
“Your cells, which are responsible for all the body processes, become less capable of doing whatever their role is in a high heat environment,” said Dr. Robert Shesser, professor and department chair of emergency medicine at George Washington University’s School of Medicine & Health Science.
It could impact the brain, the heart, and other organs in the body, he said. In some cases, cellular dysfunction from extreme heat prevents the body from using cool-down mechanisms, like sweating, which exacerbates heat-related illnesses.
Some common symptoms of heat exhaustion or heat stroke include feeling faint or dizzy, vomiting or nausea, or a rapid and weak pulse.
But extreme heat doesn’t affect everyone the same way. In patients who have chronic diseases, extreme heat tends to exacerbate their medical condition so their heat-related symptoms will just look like their chronic disease is getting worse, Shesser said.
This is why heat-related illnesses can be difficult to identify, he said, and why people tend to delay seeking help until it’s too late.
“It’s an insidious danger,” he said. “People aren’t aware that they’re becoming critically ill from heat-related illness because it kind of affects them over time.”
What is extreme heat?
Extreme heat is when summertime temperatures are much hotter or humid than average, according to the Centers for Disease Control and Prevention. This depends on what’s considered average for a particular location at that time of year.
The National Weather Service warns that “extreme heat and humidity will significantly increase the potential for heat-related illnesses, particularly for those working or participating in outdoor activities.”
This chart shows how hot it feels when the effects of humidity and high temperatures are combined:
Does heat affect some people more?
Anyone can be impacted by extreme heat regardless of age or medical conditions, but experts say certain populations are at greater risk.
Outdoor workers are at higher risk of developing heat-related illnesses because they’re typically doing strenuous activity during the hottest parts of the day. For these populations, the CDC recommends:
- Drinking plenty of water
- Wearing and reapplying sunscreen
- Scheduling tasks for earlier or later in the day to avoid midday heat
- Wearing a brimmed hat and loose, lightweight, and light-colored clothing
- Seeking refuge in air-conditioned buildings when possible
- Taking frequent breaks to cool off
Athletes are also at higher risk for similar reasons as outdoor workers. The CDC recommends people who plan to exercise outside limit outdoor activity during midday, pace their exercises and drink more water than usual. If they feel faint, it’s important to stop and get to a cool place, like shade or an air-conditioned building.
Americans 65 and up are also more likely to suffer from heat-related illnesses as the body has a harder time regulating temperature with age and older adults tend to have chronic medical conditions.
If they don’t have air conditioning, they’re also less likely to leave their house to find cooling centers, said Marcia Ory, Regents & Distinguished professor at Texas A&M School of Public Health.
It’s important for family members to be aware of the risks and know the signs of heat-related illnesses, Ory said. “Check in every day or multiple times a day to make sure your older loved one is safe and okay.”
‘Heat islands’ and what cities can do about them
“Heat islands” are urbanized areas that experience higher temperatures because of heat absorbing structures, like buildings and roads, which also re-emit the sun’s heat, according to the Environmental Protection Agency. People who live in one are also more vulnerable to heat waves and its health consequences, experts say.
“Heat islands build up heat and amplify it,” Gibbs said. They have “a lot of surfaces that build up heat, hold that heat overnight, and when the sun comes up again, it keeps amplifying.”
Daytime temperatures in “heat islands” can be up to 7 degrees Fahrenheit higher than those in outlying areas. These effects have only been exacerbated by climate change, experts say.
“People traditionally understand that it’s going to be hot in certain spots but it’s only recently that hot doesn’t mean 100 degrees Fahrenheit. Hot means 110 degrees,” Ory said.
Heat wave basicsHow to keep cool and recognize the warnings signs of heatstroke
Researchers found low-income communities or communities of color are more likely to live in certain areas within “heat islands,” called intra-urban heat islands, which run hotter than other city areas because they contain more heat-absorbing buildings and fewer cool spaces with shade and greenery.
Some cities are working to incorporate UV-resistant structures, and increase greenery and opportunities for shade, Gibbs said. Others also offer transportation to cooling centers for people who have limited access to transportation or financial assistance to those who may not be able to afford air conditioning.
“Often times, people with (low) income will forego the air conditioning in favor of fans,” he said. “But when you talk about 100-plus degrees and you talk about high relative humidity, the fan is still blowing humid air and not cooling you down as much as you think.”
Experts say more needs to be done to mitigate the extreme heat and its impact on vulnerable communities.
“What’s important is to take heat seriously. Not ten years from now, right now,” Ory said. “We have to figure out how to make the environment safer and protective from all kinds of public health disasters – heat being the latest one.”
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