The ‘urban heat island’ effect is making New Yorkers hotter, study finds

There’s a reason many New Yorkers flee the city in the summer — and it’s not just the call of the beaches.

Densely populated urban areas with tall buildings, little tree cover and lots of cars and buses tend to be hotter than rural environments, a phenomenon called the “urban heat island” effect. A new study finds that the average New Yorker feels this effect more than anyone else in the country.

New York City’s built environment is making temperatures 9.7 degrees hotter for the average resident than they would be otherwise, according to the study by the nonprofit Climate Central. That’s the biggest per capita temperature boost measured in any of the 65 cities included in the report, although not all neighborhoods feel the heat equally.

The estimated increase in temperature caused by a city’s infrastructure and activity is known as the urban heat index. Some parts of New York City have heat indexes as high as 13 degrees, while others fall below 6 degrees, Climate Central’s interactive heat map shows.

In some cases, the reason for the temperature change between areas of the city is obvious. New Yorkers strolling along Central Park’s tree-lined paths will feel a heat index of 7.5 degrees, but the heat index rises to 12 degrees for those leaving the park for nearby sections of the Upper East Side.

Even outside of green spaces like Central Park, some parts of the city fare better than others when it comes to the urban heat island effect, thanks to factors such as more tree cover and fewer tall buildings, said Jen Brady, a senior data analyst at Climate Central. Staten Island is cooler overall than Manhattan, the study found.

Some cities have even fewer pockets of relief than New York does, according to Climate Central. In Newark, 97% of the population lives in an area with an urban heat index of more than 8 degrees, compared with 83% of residents in New York City.

Research by Columbia University’s Brown Institute for Media Innovation, which was cited in Climate Central’s report, has found that communities across the country that experienced housing discrimination in the past are often subject to hotter temperatures today.

“The temperature is experienced to be around 7 degrees warmer in the redlined communities of Newark, relative to their non-redlined counterparts in Essex County,” said Michael Krisch, the institute’s deputy director, in an interview on WNYC this week. “The urban heat burden is unequally shared and it’s directly linked to this history of racially biased housing policies.”

But experts say there are still ways to cool a city down.

New York City has attempted to reduce building temperatures by painting roofs in colors that reflect heat from the sun instead of absorbing it. Brady said other solutions include longer-term ones, like planting more trees, and quicker fixes, like painting the pavement a lighter color and erecting awnings or other shade along sidewalks.