In cities across the US, people of color are enduring hotter summer temperatures than their white counterparts, new research shows. It’s another sign that the consequences of rising temperatures will hit vulnerable communities harder than others.

A person of color, on average, lives in a census tract that’s more than a full degree Celsius (nearly 2 degrees Fahrenheit) hotter in the summer than their non-Hispanic white counterparts, according to a study published today in the journal Nature Communications. That included anyone who did not identify as “white alone,” plus anyone who identifies as Hispanic. The difference in temperature was slightly larger still for Black residents.

Cities are typically several degrees warmer than more rural areas, and areas within cities without much green space are even hotter. Asphalt, cement, and dark rooftops absorb heat, while exhaust from tail pipes and industry warm neighborhoods up even more. It’s a phenomenon called the “urban heat island effect.”

Extreme heat is already the deadliest weather-related disaster in the US. The urban heat island effect and climate change are making blistering temperatures even riskier for people who live in cities. The risks are even greater for some groups, like Black Americans, who have faced a long history of housing discrimination and disinvestment. A rise in even a few degrees poses serious threats, the study’s lead author warns. The average one-degree Celsius difference in temperatures that people of color experience in America masks more extreme disparities — perhaps up to 10 degrees Celsius — that some communities face.

“That’s a lot when you translate that into real impacts and how that feels on a summertime day,” says Angel Hsu, lead author of the study and an assistant professor of public policy and the environment, ecology, and energy at the University of North Carolina-Chapel Hill.

Some neighborhoods in Hsu’s hometown of Greenville, South Carolina can see temperatures six to eight degrees Celsius higher than other parts of the city. They tended to be neighborhoods with higher proportions of Black residents. Other communities in Baltimore, Maryland got eight to ten degrees Celsius hotter than their neighbors.

The research also showed that households below the poverty line, across all racial and ethnic groups, faced more blistering temperatures than more affluent households. But the average person of color still faced hotter temperatures than their white counterparts, regardless of income.

That’s evidence that something fishy is going on with regard to race in particular, Hsu says. Other studies have suggested the same thing — Black, Asian, and Latino people are more likely to live in urban heat islands.

There’s also a long, terrible history of segregation in the US that has pushed Black Americans and other marginalized groups into specific neighborhoods. Since the 1930s, financial institutions systemically denied home loans and insurance to Black Americans. The result was “redlined” neighborhoods, where the majority of residents were Black. City planners slotted more roadways and big building complexes in and around redlined neighborhoods — and all that asphalt and concrete turned them into heat traps. Black Americans are also more likely to live near polluting industries, which can also make neighborhoods hotter. Now, these neighborhoods are up to 7 degrees Celsius hotter than other neighborhoods, according to another study published last year.

All those disparities take a deadly toll. In New York City between 2000 and 2012, African Americans made up about a quarter of the city’s population, but nearly half of its heat-related deaths.

The new study published today gives one of the most comprehensive views yet of how widespread the injustice still is. The researchers compared 2017 census data to high-resolution satellite-based temperature data for 497 urban areas in the US. They used satellite remote sensing to take stock of how surface temperatures differed between urban landscapes and more rural areas. They used that data to figure out how surfaces like asphalt made a location hotter compared to a more rural baseline. In the end, they discovered that in 169 of the 175 largest urban areas in the continental US, the average person of color lives with hotter summer daytime surface temperatures than a non-Hispanic white person.

“Something that was really surprising is how systemic this problem is. We’re not talking about one or two cities or a couple of major cities like Chicago or San Francisco. We’re talking about [this trend] in every single city,” Hsu says.

The next step, she says, is to look at a time series to figure out whether the temperature gaps between Americans of different races have gotten any better or worse over the years. She hopes that this work can identify what’s still causing these disparities and inform solutions to cool these neighborhoods down.

Looking forward, average temperatures are rising around the world because of climate change. But some places might feel the heat even more if they keep losing trees and green spaces to industrial development and urban sprawl.