Extreme heat has a way of exposing society’s vulnerabilities. And as extreme heat events become more frequent in the U.S., data shows that the poorest Americans will be most at risk.
People living in the largest, most densely populated metropolitan cities and those living in the most remote, rural parts of the country face similarly high risks during severe heat waves, an NBC News analysis of U.S. Census Bureau and U.S. Department of Agriculture data found. But while the risks are high, the reasons often differ.
Use this interactive map to explore the country and see how vulnerable the population near you is to extreme heat spikes. The map shows risk levels down to the local level and uses Census Bureau data to show the share of the population vulnerable to extreme heat, alongside data from the First Street Foundation, a nonprofit research group, to show how often an area experiences extreme heat days currently and how often it can be expected to experience them in 30 years.
Heat vulnerability assesses how many people have one of 10 risk factors the Census Bureau identified, factors that range from crowded housing conditions to lack of health insurance.
Heat causes more deaths across the U.S. each year than any other weather event, according to the National Weather Service, including tornadoes, floods and hurricanes. The Environmental Protection Agency has tracked heat-related deaths in the country since 1979, and it’s estimated that more than 600 people in the country are killed by extreme heat every year, despite heat-related deaths and illnesses being preventable, according to the Centers for Disease Control and Prevention.
With climate change making heat waves both more frequent and more intense, extreme temperatures will become part of the new reality for much of the country. In the U.S., more than 107 million people from the Great Lakes south to Texas and Louisiana could find themselves part of an “extreme heat belt” in the decades ahead.
And while no one is immune to the effects of extreme heat, not everyone faces the same risks — or consequences. Many factors can make a person more vulnerable to heat and humidity, including geographic location, socioeconomic status and overall health.
Overall, those who are most at risk for heat-related illness and death are children, older adults and individuals with pre-existing health conditions. But where a person lives can also make a big difference.
Densely populated cities tend to experience higher temperatures because buildings, roads and other human-made structures absorb and retain more heat than natural landscapes do. This is known as the urban heat island effect, and it means that urban cities can have daytime temperatures up to 7 degrees Fahrenheit warmer, and nighttime temperatures up to 5 degrees F hotter, compared with outlying areas, according to the Environmental Protection Agency.
But rural communities also face their own challenges when temperatures rise, experts say.
“Rural doesn’t necessarily mean natural,” said Kathy Baughman McLeod, director of the Adrienne Arsht–Rockefeller Foundation Resilience Center at the Atlantic Council, a Washington, D.C., think tank.
She added that many people who live in rural areas do not have access to air conditioning, particularly in their homes. Across the Southeast, in particular, the prevalence of mobile homes and manufactured housing increases the risks for many residents.
“If you’re in substandard housing with little to no air conditioning, the conditions inside may be just as hostile as outside,” Baughman McLeod said.
More than 46 million people — about 15% of the U.S. population — live in what the Census Bureau defines as rural areas. Poverty rates in rural communities also tend to be higher than in big cities. According to 2020 census bureau data, the poverty rate in nonmetro areas was 14.1%, compared with 11% in urban cities.
Ying Li, an associate professor in the College of Public Health at East Tennessee State University, said people in rural communities are more likely to work in farming and other industries that require them to be outdoors.
Li has conducted research in the past to compare rural and urban vulnerability to heat-related deaths in the U.S. and on other continents. Her work has also looked at the impact of urbanicity and socioeconomic status on heat-wave related mortality in Memphis. She said rural towns often lack the resources to help residents prepare for severe heat waves — interventions that range from subsidizing air conditioning units or opening community cooling centers.
Rural residents, as well as disadvantaged people in urban cities, tend to have less access to health care and other emergency services, which can increase heat vulnerabilities for both populations, according to experts. These groups are also more likely to have pre-existing health conditions as a result, studies have shown.
As climate change exposes people to extreme heat more frequently and for prolonged periods of time, these risks are magnified. So too are the risks when intense heat waves strike in places that historically are unaccustomed to extreme heat.
More than 200 people died in Washington state and Oregon in the summer of 2021 when a heat dome parked over the Pacific Northwest, fueling record-high, triple-digit temperatures over multiple days.
Many other communities across the country could be similarly unprepared to cope with extreme heat.
“In the southern Appalachian Mountains, traditionally people don’t have air conditioning because they always had mild summers,” Li said. “Now, it’s getting warmer. These houses never needed air conditioning, but they can get very high temperatures over the summer now.”