Over 54 degrees Celsius in some regions of the US 3:48
(CNN) -
Within cities, there are places where the summer heat can increase dramatically and giant temperature swings can be seen in a matter of blocks.
Neighborhoods with little tree cover, few grassy areas, and a lot of concrete can have temperatures between 5.5 and 11 degrees Celsius above surrounding areas.
During heat waves, these so-called 'urban heat islands' are deadly.
Extreme heat is an invisible but dangerous consequence of human-caused climate change, which kills more people per year on average than any other weather-related event, according to the National Weather Service.
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The 'urban heat island' effect amplifies the already crippling temperatures of a heat wave: areas with a lot of asphalt, buildings and highways tend to absorb energy from the sun and then radiate heat.
Green spaces such as parks, rivers, and tree-lined streets absorb less solar energy.
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And some cities face a worse situation than others.
Researchers from Climate Central, an organization that focuses on the impacts of the climate crisis, analyzed 'urban heat islands' in 158 cities in the United States and ranked the worst 20 when it comes to urban heat.
New Orleans
Newark
New York City
Houston
San Francisco
Boston
Chicago
Miami
Baltimore
Providence
Sacrament
Salinas, California
Burlington, Vermont
Bend, Oregon
Cleveland
Detroit
Erie, Pennsylvania
Fresno, California
Lafayette, Louisiana
McAllen, Texas
Andrew Pershing, director of climate science at Climate Central, said the results were somewhat unexpected.
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"Anything that includes 'urban' in the name, you are surprised if New York City and Chicago and places like that don't rank high on the list," Pershing said.
"But I was certainly surprised not to see places like Phoenix, Las Vegas, Reno on the list."
The health impacts of extreme heat
However, he said, those cities have more experience with heat and are using lighter materials to pave roads, for example, instead of black asphalt that can literally melt when temperatures are hot.
Extreme heat has multiple health impacts.
Hyperthermia, which occurs when the body cannot cool itself efficiently, can affect anyone who is exposed to extreme heat for too long.
Air pollution tends to intensify on hot days, which can irritate the lungs.
People with cardiovascular disease are particularly vulnerable in hot weather, which increases the risk of a heart attack.
This is what happens to your body in extreme heat
Recent research has shown that dark-skinned and mostly black neighborhoods suffer disproportionately from the effects of urban heat compared to their white counterparts.
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Low-income residents and communities of color tend to be in areas that lack tree coverage, green spaces and access to cooling centers, Vivek Shandas, a professor of Climate Adaptation and Urban Policy at State University, had previously told CNN. from Portland.
Many of the people in these communities have outdoor jobs, where they are exposed to heat for many hours, to pay for rent for apartments that do not have adequate cooling systems, Shandas said.
Deaths amid record temperatures
Authorities said last week that the Pacific Northwest heat wave in late June was a mass casualty situation, with hundreds of people in Oregon, Washington and British Columbia likely dying from the unprecedented temperatures.
Oregon officials say at least 83 people have died from heat-related illnesses in the state.
Of those, 54 were in the Portland area.
Many of the victims there were older, lived alone and did not have a working air conditioner, according to a preliminary report on excess heat deaths released by the county Tuesday.
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At least 78 people died in Washington, while across the border in British Columbia, officials estimate there were 500 more deaths than normal for that period - deaths they believe are heat-related.
How to plan cities to cope with heat waves?
Addressing the public health crisis requires mitigation actions during heat waves and careful planning for future development.
Pershing said that when planning new buildings or roads the color of the surfaces is essential (white is colder, black is hotter), but another interesting factor is population.
In densely populated neighborhoods, he said, there will be machinery and air conditioners that increase the heat.
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"I like to think of this as the human-induced microclimate," Pershing said.
As the climate crisis makes record heat waves increasingly frequent, researchers say cities should do more to combat the impact of urban heat islands.
They should think about how high temperatures affect before choosing materials, planting trees, and planning new green spaces.
"It's been a real problem in the development of American cities over time, (the fact that) green spaces tend to be built in the suburbs or where the rich live," Pershing said.
"I think it is very important that they are available to everyone."
CNN's Rachel Ramirez and Chris Boyette contributed to this report.