Baltimore Washington Richmond, Va. Portland, Ore. Albuquerque

As the United States suffers through a summer of record-breaking heat, new research shows that temperatures on a scorching summer day can vary as much as 20 degrees across different parts of the same city, with poor or minority neighborhoods often bearing the brunt of that heat.

“The heat island effect is often characterized as the city being hotter than surrounding rural areas,” said Vivek Shandas, a professor of urban studies and planning at Portland State University, who led heat mapping projects across the country with help from community volunteers. “We’re saying it’s a little more complicated than that.”

Buildings and paved surfaces – like major roadways, uncovered parking lots and industrial zones – amplified heat, while large parks and other green spaces cooled down the surrounding areas. In cities like Baltimore and Washington, some of the hottest temperatures were recorded in dense residential neighborhoods with little tree cover and plenty of asphalt to absorb and radiate solar energy.

As climate change makes summers hotter, the health risks associated with these hyperlocal heat islands will grow.

“This is really about human health and well-being,” Dr. Shandas said. “How do we live and thrive in these places?”

Cooler: Neighborhoods next to parks and those with plenty of tree cover saw significantly cooler temperatures on a hot summer afternoon: as low as 87°F. Hamilton Hills ROLAND Park Cylburn Arboretum Herring Run Park Druid Hill Park Hotter: On the same day, residential neighborhoods east of downtown saw hotspots reach over 101°F. Baltimore Leakin Park East Baltimore Downtown TEN HILLS Pigtown Cooler Hotter 95°F 87° 89° 92° 98° 101° 103° median temp. Hamilton Hills ROLAND Park Cylburn Arboretum Herring Run Park Druid Hill Park Hotter: On the same day, residential neighborhoods east of downtown saw hotspots reach over 101°F. Baltimore Leakin Park East Baltimore Downtown TEN HILLS Pigtown Cooler: Neighborhoods next to parks and those with plenty of tree cover saw significantly cooler temperatures on a hot summer afternoon: as low as 87°F. Cooler Hotter 95°F 87° 89° 92° 98° 101° 103° median temp. Cooler: Neighborhoods next to parks and those with plenty of tree cover saw significantly cooler temperatures on a hot summer afternoon: as low as 87°F. Hamilton Hills ROLAND Park Cylburn Arboretum Herring Run Park Druid Hill Park Baltimore Leakin Park East Baltimore Downtown TEN HILLS Pigtown Hotter: On the same day, residential neighborhoods east of downtown saw hotspots reach over 101°F. Cooler Hotter 95°F 87° 89° 92° 98° 101° 103° median temp. Cooler: Neighborhoods next to parks and those with plenty of tree cover saw significantly cooler temperatures on a hot summer afternoon: as low as 87°F. ROLAND Park Hamilton Hills Cylburn Arboretum Herring Run Park Baltimore Leakin Park East Baltimore Downtown TEN HILLS Pigtown Hotter: On the same day, residential neighborhoods east of downtown saw hotspots reach over 101°F. Cooler Hotter 95°F 87° 89° 92° 98° 101° 103° median temp. Cooler: Neighborhoods next to parks and those with plenty of tree cover saw significantly cooler temperatures on a hot summer afternoon: as low as 87°F. Hamilton Hills ROLAND Park Baltimore Leakin Park Downtown TEN HILLS Hotter: On the same day, residential neighborhoods east of downtown saw hotspots reach over 101°F. Cooler Hotter 95°F 87° 89° 92° 98° 101° 103° median temp.

Baltimore

Afternoon range: 87°F to 103°F

To map Baltimore’s heatscape, Dr. Shandas’s team and local volunteers recorded street-level temperatures during one of the hottest days of the year last summer. They got a maximum reading of nearly 103 degrees in the city’s downtown, an area of large brick buildings, parking lots and few trees. The lowest temperature, 87 degrees, was recorded in a forested part of the Ten Hills neighborhood.

A conspicuous belt of high heat stretched east of downtown, across residential neighborhoods made up of dense row houses, typically with no yards and little tree cover. Average temperatures in this area, which is majority African American and largely lower-income, hovered between 98 and 99 degrees, with hot spots reaching as high as 102 degrees.

At the same time, average temperatures in the more affluent, tree-lined residential areas in the city’s north, as well as those surrounding Leakin Park to the west, stayed in the low 90s.

High heat: Rowhouses with sparse tree cover in McElderry Park, East Baltimore. Cooler temperatures: Franklintown, a historic neighborhood near Leakin Park.

High heat: Downtown Baltimore. Cooler temperatures: The residential Roland Park neighborhood in North Baltimore. All photos by Rosem Morton for The New York Times

Baltimore is trying to ease the heat burden by planting more trees. The city plans to increase its tree canopy to cover 40 percent of the city, up from 28 percent in 2015, according to Lisa McNeilly, director of the Baltimore Office of Sustainability.

The city is also trying to turn some of its vacant lots into permanent green spaces. When abandoned or derelict homes are demolished, the land beneath them is sometimes used for parking. But by turning those lots into small parks, Ms. McNeilly said, Baltimore can increase the amount of vegetation and make neighborhoods cooler.

But those changes take time. Meanwhile, city officials are working to open more community cooling centers to give more people without air-conditioning a way escape the heat. “This is less about reducing how hot it is, and more about what we’re doing to help the community be more resilient to it,” Ms. McNeilly said.

Cooler: Forested Rock Creek Park recorded the city’s lowest temperatures and helped to cool down surrounding areas. Hotter: Hotspots in Brookland, Columbia Heights and LeDroit Park hit 100 to 102°F. Rock Creek Park Cleveland Park Columbia heights Palisades Brookland Ledroit Park Downtown Washington, D.C. Average temperatures hovered in the low 90s in the affluent Palisades neighborhood, with cool spots as low as 87°F. Capitol Hill Fort Circle Park Fort Circle Park Anacostia Cooler Hotter 94°F 85° 88° 91° 97° 100° 102° median temp. Cooler: Forested Rock Creek Park recorded the city’s lowest temperatures and helped to cool down surrounding areas. Rock Creek Park Hotter: Hotspots in Brookland, Columbia Heights and LeDroit Park hit 100 to 102°F. Cleveland Park Columbia heights Palisades Brookland Ledroit Park Downtown Washington, D.C. Average temperatures hovered in the low 90s in the affluent Palisades neighborhood, with cool spots as low as 87°F. Capitol Hill Fort Circle Park Fort Circle Park Anacostia Cooler Hotter 94°F 85° 88° 91° 97° 100° 102° median temp. Cooler: Forested Rock Creek Park recorded the city’s lowest temperatures and helped to cool down surrounding areas. Hotter: Hotspots in Brookland, Columbia Heights and LeDroit Park hit 100 to 102°F. Rock Creek Park Columbia heights Palisades Brookland Downtown Washington Average temperatures hovered in the low 90s in the affluent Palisades neighborhood, with cool spots as low as 87°F. Fort Circle Park Anacostia Cooler Hotter 94°F 85° 88° 91° 97° 100° 102° median temp. Cooler: Forested Rock Creek Park recorded the city’s lowest temperatures and helped to cool down surrounding areas. Hotter: Hotspots in Brookland, Columbia Heights and LeDroit Park hit 100 to 102°F. Rock Creek Park Columbia heights Palisades Brookland Downtown Washington Average temperatures hovered in the low 90s in the affluent Palisades neighborhood, with cool spots as low as 87°F. Fort Circle Park Anacostia Cooler Hotter 94°F 85° 88° 91° 97° 100° 102° median temp.

Washington

Afternoon range: 85°F to 102°F

In Washington, the heat island effect closely matches the city’s social and economic divisions. Neighborhoods to the west of Rock Creek Park, which are predominantly white and have some of the city’s highest-value homes, were significantly cooler than the northeast section, on the other side of the park.

“The northeast part of the city is an area that we still have zoned for industrial uses,” said Tommy Wells, director of Washington’s Department of Energy and Environment. “You can have large stretches of low-slung buildings with large parking lots that retain heat.”

Like Baltimore, Washington has a goal of covering 40 percent of the city with tree canopy, Mr. Wells said. But the city’s most effective tool to fight heat islands could be the pace of new development.

As decades-old industrial sites are replaced by condos, restaurants or other structures, those new buildings have to comply with the city’s current regulations for capturing rain that falls on their property, limiting the water running into Washington’s overtaxed storm drains. Meeting those rules often involves significant green space around or on top of buildings.

“The transformation of our city, meeting our stormwater marks, will cool the city,” Mr. Wells said. “The more development we have going on, the more I can meet the goals of greening the city.”

Hotter: Afternoon temperatures over 100°F were found along Arthur Ashe Boulevard, a major artery cutting through industrial and quickly gentrifying neighborhoods down to the Fan District. Wilton fan district James River Park Oakwood Cemetery Powhite Park Cooler: At the same time, neighborhoods around Powhite Park saw temperatures as low as 87°F. Old town manchester Richmond Cooler Hotter 95°F 87° 89° 92° 98° 102° median temp. Belmont woods Hotter: Afternoon temperatures over 100°F were found along Arthur Ashe Boulevard, a major artery cutting through industrial and quickly gentrifying neighborhoods down to the Fan District. Wilton fan district James River Park Oakwood Cemetery Powhite Park Cooler: At the same time, neighborhoods around Powhite Park saw temperatures as low as 87°F. Old town manchester Richmond Belmont woods Cooler Hotter 95°F 87° 89° 92° 98° 102° median temp. Hotter: Afternoon temperatures over 100°F were found along Arthur Ashe Boulevard, a major artery cutting through industrial and quickly gentrifying neighborhoods down to the Fan District. Wilton fan district James River Park Oakwood Cemetery Powhite Park Old town manchester Cooler: At the same time, neighborhoods around Powhite Park saw temperatures as low as 87°F. Richmond Belmont woods Cooler Hotter 95°F 87° 89° 92° 98° 102° median temp. Hotter: Afternoon temperatures over 100°F were found along Arthur Ashe Boulevard, a major artery cutting through industrial and quickly gentrifying neighborhoods down to the Fan District. James River Park fan district Powhite Park Old town manchester Richmond Cooler: At the same time, neighborhoods around Powhite Park saw temperatures as low as 87°F. Cooler Hotter 95°F 87° 89° 92° 98° 102° median temp.

Richmond, Va.

Afternoon range: 87°F to 102°F

The health consequences of heat islands can be profound. Jeremy S. Hoffman, chief scientist at the Science Museum of Virginia, who worked with Dr. Shandas on the heat mapping project, compared average temperatures for Richmond zip codes to data on heat-related illnesses. He found that the four warmest ZIP codes also saw the highest rates of heat-related ambulance calls and emergency room visits.

Richmond’s heat islands also overlap with its communities of color and low income, according to Brianne Mullen, the city’s sustainability coordinator. The city has just two cooling centers, and, because of budget cuts, the number of trees planted fell drastically in 2016 and 2017 before rebounding last year.

Ms. Mullen said the city was still in the “early days” of coming up with a strategy to address its heat islands and was updating its master plan to account for the problem. “It’s an issue very present in people’s minds right now,” she said.

Hotter: Temperatures along Interstate Avenue in the Overlook neighborhood reached 93°F. An industrial area to the south framed by highways hit 95°F. Smith Lake St. Johns airport Forest Park OVERLOOK Rocky Butte Natural Area Portland Down town Cooler: Portland’s massive Forest Park provides an 8-mile stretch of cooler temperatures on the city’s west side. Residential neighborhoods to its south remained in the mid-80s, with cool spots dipping below 78°F. Mt. Tabor Park Lents Powell Butte Nature Park Tryon Creek Natural Area Cooler Hotter 89°F 77° 80° 83° 86° 92° 95° median temp. Hotter: Temperatures along Interstate Avenue in the Overlook neighborhood reached 93°F. An industrial zone to the south framed by highways hit 95°F. St. Johns airport Forest Park OVERLOOK Rocky Butte Natural Area Portland Down town Mt. Tabor Park Cooler: Residential areas to the south of Portland’s massive Forest Park remained in the mid-80s on a hot summer afternoon, with cool spots dipping below 78°F. Lents Powell Butte Nature Park Tryon Creek Natural Area Cooler Hotter 89°F 77° 80° 83° 86° 92° 95° median temp. Hotter: Temperatures along Interstate Avenue in the Overlook neighborhood reached 93°F. An industrial zone to the south framed by highways hit 95°F. St. Johns airport Forest Park OVERLOOK Rocky Butte Natural Area Portland Down town Mt. Tabor Park Cooler: Residential areas to the south of Portland’s massive Forest Park remained in the mid-80s on a hot summer afternoon, with cool spots dipping below 78°F. Lents Powell Butte Nature Park Tryon Creek Natural Area Cooler Hotter 89°F 77° 80° 83° 86° 92° 95° median temp. Hotter: Temperatures along Interstate Avenue in the Overlook neighborhood reached 93°F. An industrial zone to the south framed by highways hit 95°F. St. Johns Airport Overlook Forest Park Portland Lents Powell Butte Nature Park Cooler: Residential areas to the south of Portland’s massive Forest Park remained in the mid-80s on a hot summer afternoon, with cool spots dipping below 78°F. Cooler Hotter 89°F 77° 80° 83° 86° 92° 95° median temp.

Portland, Ore.

Afternoon range: 77°F to 95°F

Portland’s huge Forest Park provides an oasis of cool along the city’s west side. Two residential neighborhoods south of that park, Sylvan-Highlands and Southwest Hills, registered some of the lowest afternoon temperatures on a hot summer day, dipping as low as 78 degrees.

At the same time, hot spots on the east bank of the Willamette River reached well into the 90s. Some of the hottest areas are industrial, marked by warehouses, parking lots and few trees, according to Michele Crim, the city's chief sustainability officer. The same is true for the bank the Columbia River, which forms the city's northern border.

Hot areas dotted Interstate Avenue in the Overlook neighborhood, with afternoon highs reaching into the mid-90s. An industrial stretch along the neighborhood’s south showed a maximum of 95 degrees. Highway 205, and the businesses that surround it, appear as a red streak running vertically from the city’s southern boundary, through the Lents neighborhood and up to the cooler Rocky Butte Natural Area.

High heat: Near the Moda Center, a sports arena bracketed by large roadways like Interstate 5. Cooler temperatures: The residential Arlington Heights neighborhood in West Portland. All photos by Amanda Lucier for The New York Times

Portland has proposed new requirements for multifamily housing and apartment buildings to reduce the amount of pavement. Those proposals include limiting the amount of a new development set aside for parking to just 30 percent of the total surface area of a given property. No more than half of that could be covered with asphalt, which has even greater heat-trapping effects than concrete or other hard surfaces.

The change would also require more green space, for instance by requiring landscaped space between buildings and the street.

Cooler: The lowest temperatures were found at the edge of the city's Northeast Heights area, which is cooler than downtown thanks in part to its higher elevation. No data Petroglyph National Monument Northeast Heights Downtown Albuquerque Hotter: Albuquerque’s most prominent hotspot was located downtown, with temperatures over 100°F recorded surrounding the city’s central train and bus stations. Cooler Hotter 94°F 88° 91° 97° 100° median temp. Cooler: The lowest temperatures were found at the edge of the city's Northeast Heights area, which is cooler than downtown thanks in part to its higher elevation. No data Petroglyph National Monument Northeast heights Downtown Albuquerque Hotter: Albuquerque’s most prominent hotspot was located downtown, with temperatures over 100°F recorded surrounding the city’s central train and bus stations. Cooler Hotter 94°F 88° 91° 97° 100° median temp. Cooler: The lowest temperatures were found at the edge of the city's Northeast Heights area, which is cooler than downtown thanks in part to its higher elevation. No data Petroglyph National Monument Northeast Heights Downtown Hotter: Albuquerque’s most prominent hotspot was located downtown, with temperatures over 100°F recorded surrounding the city’s central train and bus stations. Albuquerque Cooler Hotter 94°F 88° 91° 97° 100° median temp. Cooler: The lowest temperatures were found at the edge of the city's Northeast Heights area, which is cooler than downtown thanks in part to its higher elevation. No data Petroglyph National Monument Northeast heifghts Albuquerque Downtown Hotter: Albuquerque’s most prominent hotspot was located downtown, with temperatures over 100°F recorded surrounding the city’s central train and bus stations. Cooler Hotter 94°F 88° 91° 97° 100° median temp. Cooler: The lowest temperatures were found at the edge of the city's Northeast Heights area, which is cooler than downtown thanks in part to its higher elevation. Albuquerque No data Northeast Heights Down town Hotter: Albuquerque’s most prominent hotspot was located downtown, with temperatures over 100°F recorded surrounding the city’s central train and bus stations. Cooler Hotter 94°F 88° 91° 97° 100° median temp.

Albuquerque

Afternoon range: 88°F to 100°F

In Albuquerque, heat patterns are partly a function of topography, according to Kelsey Rader, the city’s sustainability officer. The city sits in a rift valley between the Rio Grande and the Sandia Mountains; the difference in temperature generally follows the change in elevation, as the land rises from the river to Albuquerque’s eastern edge.

“Everything slopes downward toward the Rio Grande,” Ms. Rader said. “Often you’ll see about a five-degree difference for neighborhoods that are sitting on the outskirts.” But the map also shows how the built environment can influence those patterns: The city’s dense downtown core is hotter than the riverbank to its west, with the highest temperatures recorded around the train station.

Albuquerque’s dry climate doesn’t suit green roofs, according to Ms. Rader, so the city is fighting the heat-island effect by requiring new buildings to use roofing materials that reflect most of the sun’s energy. It has also installed arrays of solar panels at the airport and zoo; those panels create energy to charge electric vehicles, but they also reduce the amount of sunlight that reaches the surface of the parking lot.

The easiest answer for cities that want to fight heat islands is straightforward, according to Dr. Shandas: More green and less pavement.

“If there’s anything a city can do, it’s to rethink how much roadway it’s going to put down,” he said. “What are the places you could potentially de-pave?”