Extreme Heat Is Getting Worse for Low-Income, Non-White Americans, New Study Finds

As record-high heat hammers much of the country, a new study shows that in many American cities, residents of lower-income neighborhoods and communities of color often endure far higher temperatures than those who live in whiter, wealthier communities.

Urban areas are known to be hotter than more rural ones, but the research published Tuesday in the journal Earth's Future provides one of the most detailed looks to date at how differences in heat extremes break down along racial and socioeconomic lines.

The authors used satellite imagery to measure land surface temperature in 1,056 counties across the country, home to about 300 million people. They found that in more than 70% of those counties, neighborhoods that are lower income and those that have larger percentages of people of color "experience significantly more extreme surface urban heat than their wealthier, whiter counterparts."

Relying on U.S. census data, the researchers found that in areas with higher rates of poverty, temperatures can be as much as 7 degrees Fahrenheit warmer during the summer months than in nearby wealthier neighborhoods. The same held true for predominantly minority communities, as compared to nearby non-Hispanic, white neighborhoods.

The study is the latest to show how climate change driven by human activity disproportionately harms people of color and poor people. The warming climate is making heat waves more frequent and intense. And even without heat waves, Americans can expect far more days over 90 degrees Fahrenheit than there were just a few decades ago.

Heat is the biggest weather-related killer of Americans, according to the U.S. Environmental Protection Agency; an estimated 800 people have already died in the heat wave that has gripped the Pacific Northwest this month.

The researchers — Susanne Benz and Jennifer Burney of UC San Diego — found that in 76% of the counties they studied, lower-income communities experienced higher temperatures than those with higher incomes. When looking at neighborhoods by race, in 71% of counties, people of color lived in neighborhoods with higher temperatures than residents in largely white communities.

The researchers point to several factors that are driving up temperatures in these neighborhoods, including more buildings, less vegetation, and to a lesser extent, higher population density.

Previous studies have shown that less vegetation can impact a city's temperature, and that neighborhoods that are lower income and where there are more people of color tend to have less tree cover.

The researchers also note that the temperature differences they found weren't unique to larger, more developed cities; heat disparities were also evident in many smaller, more rural areas with newer developments.

"The existence of these gradients implies that the inequality we find in our cities does not only develop after large urbanization and growth, but manifests early in the existence of a city itself," the report states.

Its authors also point to a long history of racist land-use policies that have driven such disparities, and urge local policymakers to make equitable development decisions that incorporate heat mitigation strategies, among other factors.

"These areas have less tree canopy, more streets, and higher building densities," the authors contend, "meaning that in addition to their other racist outcomes, redlining policies directly codified into law existing disparity in urban land use and reinforced urban design choices that magnify urban heating into the present."

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KQED's Matthew Green contributed reporting to this story.