A new report says more than 40 million Americans are living in areas that are at least 8 degrees hotter than other areas in their city because they’re in a heat island.
As nearly 40% of the U.S. population faces heat advisories this week, people in urban areas are more likely to experience higher temperatures -- and New York City has the highest average of the urban heat island (UHI) index out of 44 large cities that were analyzed by Climate Central.
That means that on a 90°F day in rural upstate New York, people living or working in downtown Manhattan with a UHI index value of 8.6°F would experience temperatures of at least 98.6°F.
The city of Newark came in second (8.4°F) when the UHI index values were averaged by the city’s total area, according to the analysis released Wednesday by the nonprofit group of scientists. The average UHI index per capita was lowest in Wichita (7.2°F) and highest in NYC (9.5°F), followed by San Francisco (8.8°F), Chicago and Miami (8.3°F), and Seattle (8.2°F), according to the analysis.
But what makes the heat so much worse (about 15-20 degrees) in our cities compared to rural areas, and what can be done to alleviate the extreme heat that's expected to worsen due to climate change?
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The urban heat island effect
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Cities are generally hotter due to the simple fact that about 85% of people in the country live in metropolitan areas, according to the National Climate Assessment.
When you add on the number of buildings and other hard, dark surfaces that reflect back sunlight, the heat gets worse. Those reflections are called albedo, and they're considered the largest influence on what is known as the urban heat island effect.
Other aspects of city life such as the heating and cooling of said buildings, transportation, and industrial facilities are also contribute to the urban heat island effect. According to Climate Central, air conditioning can add 20% more heat to the outside air.
The designs of each city also play a huge role in how these hot spots are distributed, Climate Central's analysis found. New York City and Newark are considered to be dominated by sprawling heat intensity, meaning that high UHI index values are not concentrated in one area but rather spread out.
Some cities like Philadelphia, Albuquerque and Las Vegas have concentrated heat intensity at their urban core.
In Atlanta, Chicago and Boston, there are diffused zones of heat intensity.
Heat inequality in NYC
While New York City is considered one of the cities with sprawling heat intensity, city officials say there are still parts of the city that are hotter than others.
According to satellite data collected by the City Council's Data Operations Unit, south and southeast Brooklyn and southeast Queens experience higher temperatures compared to the rest of the five boroughs.
Map: New York City Council Data
According to a 2021 report the U.S. Environmental Protection Agency, Black Americans are 40% more likely than non-Black Americans to live in areas with the highest projected increases in extreme temperature-related mortality. The analysis also found that low-income and Hispanic or Latino populations are also disproportionately exposed to extreme heat.
The heat inequity is apparent by taking a look at access to air conditioning. The New York City Council found that residents in Brownsville, Jamaica, Rockaways, East Tremont, and Mott Haven/Hunts Point experience extreme heat and relatively less access to air conditioning. The residents of these neighborhoods are largely Black and Hispanic, according to the city's census.
What can be done to make cities less hot?
Plant more trees. Trees help remove air pollutants that can trigger respiratory illnesses, reducing stormwater run-off
keeping the city cooler, providing shelter and food for wildlife, and even help reducing energy used by buildings, according to the Parks Department.
Green roofs, cooling roofs and cooling pavements can also help cities relieve some of the heat, Climate Central's analysis said.
To address short-term solutions like unequal access to air conditioning, the City Council aims to target home cooling support programs and cooling center locations in the most affected areas.
Click here to see safety tips during extreme heat. And click here to know the warning signs of heat stroke and other heat-related illnesses.
