As Another Hot Summer Approaches, 80 New York City Neighborhoods Ranked Highly Vulnerable to Heat

NEW YORK—Outside the steps of her South Bronx apartment, Jill Hanson is thinking about the lack of green spaces as another hot summer descends upon New York City. Her neighborhood, Mott Haven, is among 80 communities considered highly threatened by humidity and high temperatures under a new Heat Vulnerability Index developed by Columbia University and the city’s Department of Health and Mental Hygiene.  

“We’re always cited as being one of the worst neighborhoods for the heat index problems and for not having any street trees,” said Hanson, 60, an architect. “So, I don’t really get why we can’t just get more street trees if the whole city is getting street trees.”

Hanson, who is white and owns her own apartment, said living in a low-income section of New York makes clear to her how poor city planning over the years has created barriers to green space in the South Bronx. 

Coming off New York’s hottest year on record, as climate change amplifies risks related to high heat and heightens the disproportionate impacts on low-income neighborhoods and communities of color, a new city report shows that more than 60 percent to 70 percent of residents in the most heat vulnerable neighborhoods live in such “environmental justice” communities. 

The 2024 Environmental Justice Report, published by the Mayor’s Office of Climate and Environmental Justice, found that Black New Yorkers are two times more likely to die from heat stress as White New Yorkers, and that Black residents are also less likely to have access to air conditioning, “the most effective way to prevent heat-health impacts.” 

Mayor Eric Adams, during the launch of a city-wide “Beat The Heat” campaign last week, cited the report’s finding that heat-related deaths averaged 350 per year from 2011 to 2020, and that from 2017 to 2022, the city averaged 683 emergency room visits by those suffering from heat-related illness. 

And all projections are that climate change will only make the threat much worse in the coming decade.

From 2016 to 2020, there was an average of 17 days a year over 90 degrees Fahrenheit and 11 “extreme heat events,” defined as two or more days with a heat index of 95 degrees, or one or more days reaching 100. “In an average year in the 2030s, there are projected to be up to three times as many days with temperatures over 90 degrees Fahrenheit and up to nearly four times as many heat waves as there have been in the recent past,” the report says. 

The city’s vulnerability to heat is heightened by the urban heat island effect, the report says, “a phenomenon that can lead to cities being up to 22 degrees Fahrenheit hotter than rural and suburban areas due to the amount of dark impervious surfaces, limited vegetation, and dense human activity.” 

In Mott Haven, a mostly residential neighborhood in the southwestern Bronx, Hanson has planted trees in her yard to mitigate the heat, reflecting the grassroots work of South Bronx Unite and residents to combat the heat island effect. 

According to the city’s Heat Vulnerability Index, a statistical model, Mott Haven has a score of five, the highest, based on four factors—surface temperatures, green space, access to home air conditioning and the percentage of low-income or non-Latinx Black residents. The neighborhood’s median income is just $24,474. Citywide, the median household income in New York City is $74,694. 

While Hanson is fortunate to have central air conditioning, many of her neighbors do not. She attributes air pollution in the neighborhood to big warehouses in the area and heavy traffic. 

“We need less big business on the edges taking over the potential green space,” Hanson said, noting that she’s lived in Mott Haven for the last eight years. Before that she said she lived in Lower Manhattan and has come to see stark socioeconomic differences between Mott Haven and her old neighborhood. 

In his “Beat the Heat” announcement last week, Mayor Adams said that the city’s Department of Parks and Recreation will be planting a total of 18,000 trees, prioritizing heat vulnerable neighborhoods like Mott Haven. 

After the city launched a $106 million Cool Neighborhoods program in 2017, Adams announced in 2022 that an additional $112 million would be spent on expanding the city’s tree canopy and other heat-reducing strategies. The city’s environmental justice report says the parks department “will fulfill all potential tree-planting opportunities in every neighborhood with a Heat Vulnerability Index score of four or higher” by 2027. In total, there are 40 neighborhoods with a Heat Vulnerability Index score of five and another 40 with an HVI score of four. 

Mike Treglia, lead scientist for the Nature Conservancy’s New York State Cities Program, said in an interview that heat vulnerable neighborhoods will need additional tree canopy the size of seven baseball fields to reach 32 percent vegetation cover to benefit from cooler temperatures. 

“Heat vulnerabilities are really multifaceted and alleviating the Urban Heat Island Effect is a really important part of the equation,” Treglia said. “And, we want to achieve equity of canopy and vegetation.” 

Samantha Irvin, who grew up in Central Harlem and now lives in the Bronx neighborhood of Highbridge, was surprised to learn that both neighborhoods, environmental justice communities, are considered high-risk areas for heat-related illnesses or deaths due to extreme heat. 

But Irvin, 37, a Black woman working in human resources, is aware of how the Urban Heat Island Effect impacts millions of New Yorkers every summer. Almost daily, Irvin rides the subway or walks over the Harlem River to check on her mother, 66, and godmother, 80, who live in Harlem, to make sure they’re cool during the summer or warm in the winter. 

“I make sure that if they need something, they have it,” Irvin said. “I would be worried about those older folks who do not have a caretaker or someone to help them or family members checking in because the house can get hot.” For her apartment, Irvin says she is mindful of AC  use because of how it drives up utility costs, and because she enjoys the hotter weather, she does her best to work around AC usage. At her mom’s place, she also makes sure to be mindful of AC use, along with utility costs. 

Residents of Central Harlem, which is in Upper Manhattan, are significantly below the city average for having access to air conditioning. The neighborhood has a median income significantly below the city average, too. Irvin’s Highbridge neighborhood has an HVI score of four that is driven by two factors: median income and access to air conditioning units. But the score isn’t five because Highbridge has more greenspace and a cooler temperature than the city average. 

Jeffrey Schlegelmilch, an associate professor and director of the National Center for Emergency Preparedness at Columbia’s Climate School, said that while the Heat Vulnerability Index is a tool to understand disaster vulnerability across the city, it’s also a means for understanding the impacts of racial redlining across neighborhoods. 

“When we think about disasters, we think about exposure, which a lot of times comes from the investment that’s been made in the neighborhoods,” Schlegelmilch said, explaining that the legacies of urban planning have played a role in how much green space neighborhoods enjoy.