It was so hot in Nubian Square Thursday afternoon that the humid air in Roxbury wasn’t just palpable, it was visible — hovering in blurry waves radiating over the asphalt. It was similarly steamy near Maverick Square in East Boston, where a warren of old brick buildings and few trees combined to make the heat wave feel unbearable.
It was also hot in the Longwood neighborhood of Brookline, but in a park filled with century-old beech trees and surrounded by the manicured lawns of multimillion-dollar homes, the temperature was discernibly cooler, if only slightly, according to thermometer readings by Globe reporters who fanned across the city on the second day of the heat wave.
As climate change brings more hot days to the area, those small differences can be significant, and they’re likely to become increasingly pronounced, especially in lower-income neighborhoods where there are fewer trees, more concrete, and less air conditioning, a growing body of research shows. The worst temperature differences are in humid cities including Boston along the East Coast, according to the Environmental Protection Agency.
By the end of the decade, temperatures in Boston could exceed 90 degrees for more than 40 days a year — and for as many as 90 days annually in 2070 — compared with an average of four days between 1971 and 2000, according to city projections. Those increases in temperatures could have serious health consequences, with one major study estimating that heat-related deaths in the coming decades could be more than 50 percent higher than they were a few decades ago.
In an effort to observe differences in the way the latest heat wave affected Boston’s neighborhoods, the Globe equipped six reporters with store-bought window thermometers and sent them to different corners of the city on Thursday, at the heat wave’s height. They measured temperatures at 3 in the afternoon and 10 at night, employing standard procedures used to gather official temperatures — several feet above the ground, in the shade. While it was not a scientific study by any stretch, what emerged was a snapshot of a sweltering city.
They found that the afternoon temperatures were highest — 97 degrees — in Roxbury and East Boston; they were 2 degrees cooler in Brookline and in the Fields Corner neighborhood of Dorchester. They were the lowest in the leafy meadows of Franklin Park, at 93 degrees. At night, the temperatures were more uniform, but the disparity remained 4 degrees, ranging from a high of 83 to a low of 79 in Franklin Park.
When city officials conducted a similar survey in July 2019, they found more dramatic results: Afternoon temperatures in Chinatown and Lower Roxbury exceeded 105 degrees, about 10 degrees more than in Franklin Park and West Roxbury. There was a similar disparity at night.
On Thursday afternoon in Roxbury’s Nubian Square, Peggy Rechemond, who was hanging out with a friend who sells hats from a tent, was fanning herself as beads of sweat glistened on her forehead.
“Sometimes my stomach hurts because it’s so hot,” said Rechemond, 49, of Mattapan, whose heart murmur and high blood pressure require that she doesn’t exhaust herself on days like this.
At Central Square Park in East Boston, Manny Castello was seeking refuge from the heat on a shaded bench, hoping to give his overworked air conditioner at home a break.
“Over there, you’ll burn yourself,” he said, pointing to the edge of the park.
In Allston, along the intersection of Commonwealth Avenue and Harvard Street, the temperatures were slightly cooler. Still, at 93 degrees at 3:15 p.m., with asphalt just about everywhere, the breeze carried clammy air.
“I feel like I’m hiding from the world,” said Jalen Benson, 26, a medical student walking through the neighborhood.
Benson had invited a group of classmates to his house the night before, because his apartment has central air. But he’s moving in a few weeks to a place without that luxury.
“It’s very scary, because a heat wave now means terrible, terrible global warming,” he said.
A few months ago, city officials issued a report about how the hottest parts of Boston are concentrated in lower-income neighborhoods. It noted that the disparity could be attributed to the city’s history of racial inequity, in which banks “redlined” certain neighborhoods, making it difficult for people of color to obtain mortgages and leaving those neighborhoods with less green space and other public investments.
In the report, officials noted that those neighborhoods, once determined by banks to be “hazardous” for loans, are now 3.3 degrees warmer than the city’s average, nearly 2 degrees warmer at night, with 16 percent less parkland and 7 percent fewer trees. The neighborhoods the banks considered the “best” or “desirable” tend to be 4.2 degrees cooler during the day than the city average and 1.7 degrees cooler at night, with 4 percent more parkland and 32 percent more trees.
“Historically, we’ve made decisions that have led to these inequities, and now we need to work collaboratively to balance the scales,” Reverend Mariama White-Hammond, the city’s environment chief, told the Globe shortly after the report was released. “We have to do this not just for what is happening now, but for what we know is coming down the line.”
Among those disturbing trends are not only warmer afternoons but warmer nights, meaning city residents are less likely to get even a brief reprieve during heat waves.
The average minimum temperature for summer has warmed on average nearly 4 degrees since 1872, said Jennifer Brady, a researcher at Climate Central, a New Jersey-based group that advocates for government action to address climate change.
As the afternoon waned in Franklin Park, where many of the city’s residents throng for the relatively cooler temperatures, Elenah Creech did her best to beat the heat, sitting with her grandmother and friends in a shady spot they frequent along Circuit Drive.
The 11-year-old from Grove Hall wasn’t looking forward to returning home, which not only lacks air conditioning but also fans, she said.
As she sat in a camping chair, scrolling on her phone, she periodically got up to cruise around on her electric scooter.
“The breeze helps,” she said. “My back is literally drenched in sweat.”
A few chairs away, as the temperature slowly dropped to 92 degrees, Bobby Lighty sipped from a frozen water bottle.
Despite the traffic on the nearby road, he was content, no matter the heat.
“It’s hot, but this is a good place to be,” he said, pointing to all the trees and rolling hills on the golf course across the street. “We’re getting by.”
Zoe Greenberg, Gal Tziperman Lotan, and Laura Krantz of the Globe Staff and Globe Correspondents Kate Lusignan and Julia Carlin contributed to this report.