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Extreme Weather Climate

The Heat Island Effect: See How Trees Can Combat Rising Temps

Excessive heat is becoming deadly. But trees in the right place stand strong to shield communities.

June 17, 2026
Person wearing a helmet rides a bicycle on a tree-lined path in a sunlit park with benches and greenery around.

Across the country, one fact is becoming impossible to ignore: It’s hot — and it’s getting hotter.

Record-breaking heatwaves have Americans experiencing the effects of extreme heat more than ever before. In cities as geographically diverse as Phoenix, Miami, and New York, the number of days topping 100°F has doubled or even tripled over the past 30 years. And according to the National Oceanic and Atmospheric Administration (NOAA), Earth’s 10 hottest years on record have all occurred within the last decade. 

This isn’t a looming scenario. It’s a shared American reality — one that’s quickly shifting from uncomfortable to unbearable. 

urban heat island illustration

What is the heat island effect?

The urban heat island effect is a phenomenon in built-up cities and towns caused by heat-trapping surfaces like concrete and asphalt. These materials absorb the sun’s energy and radiate it back into the air, raising temperatures by as much as 20°F compared to surrounding rural areas. 

Extreme heat is now the deadliest weather-related disaster in the U.S., killing more Americans each year than hurricanes, floods, and wildfires combined. While heat can be dangerous for all Americans, more than 100 million live in areas in need of greater tree canopy. That’s nearly a third of the population. It’s why planting trees is a critical tool to keep communities healthy and resilient as they face increasingly hot and severe weather.

Keeping communities cool and safe is why we plant trees from coast to coast.

Swipe through snapshots from some of our tree planting projects in communities to help tame heat.

A group of volunteers plants a tree in Baltimore, MD, using shovels and wearing gloves on a sunny autumn day.
In neighborhoods with as little as 6% canopy — far below the city's average of around 28% — tree plantings are critical to cool urban heat islands and promote equitable public health.
Three people planting a young tree in a garden, with one person adding soil and another holding a pot, set in Bridgeport, CT.
In East Bridgeport, our partners plant trees to mitigate heat in areas with as little as 5% tree coverage.
Two people are planting trees and shrubs along a street in Brooklyn, NY, with traffic cones and a parked car in the background.
Local planting partners are working to close the canopy gap in neighborhoods that have long gone without green investment. 
A group of volunteers in matching shirts gathers for a planting activity in Buckeye, AZ, with a focus on community service.
In this fast-growing desert city — recording 181 days above 90 °F annually — limited tree cover drives extreme heat; targeted plantings provide essential shade in new developments.
A group of volunteers walks along a pathway in Chicago, carrying tools and buckets, with a colorful mural on the wall beside them.
Many South and West Side communities face canopy levels well below the city average (~17 %), suffering higher heat impacts — new trees are bringing much-needed cooling relief to community members.
Group of volunteers planting a young tree in a park in Cincinnati, OH, surrounded by greenery and playground equipment.
Aging canopy and urban sprawl have left parts of the city with sparse shade; recent community-led plantings aim to revitalize streets and reduce summer heat islands.
Three individuals in green shirts engage in planting a small tree outside a building in Glendale, AZ, under a clear blue sky.
New trees are being planted in heat-prone cities, like Glendale, to bring shade and resilience to neighborhoods where concrete and asphalt dominate the landscape.
A group of volunteers is planting a tree in a grassy area under clear blue skies in Greenville, SC. Shovels and tools are scattered around.
Local partners join forces to plant trees where canopy is low and the need for cooling shade is high.
Three individuals participate in a community tree planting event in Jacksonville, FL, surrounded by grass and a chain-link fence.
With soaring summer temps and limited shade in older urban corridors, tree plantings help curb energy costs and protect vulnerable populations from heat stress.
Two individuals actively digging in the ground, surrounded by a group of onlookers in a sunny park setting in Mesa, AZ.
Mesa is one of Phoenix metro’s hottest suburbs, with surface temps routinely exceeding 150 °F on pavements. Planting shade trees offers relief and helps cool streets and public areas.
Two volunteers plant a young tree in Miami, FL, surrounded by soil and lush greenery, with fellow volunteers working in the background.
Miami partners are turning to trees as a powerful tool to cool streets, lower energy costs, and improve lives.
A diverse group of individuals gather outdoors in Nashville, TN, facing an organizer while holding shovels under a bright, sunny sky.
Nashville has lost hundreds of acres of canopy in recent years, due to urban development, storm damage, and invasive species.
A group gathers in Oklahoma City for a tree planting demonstration, featuring a speaker with a sapling and participants engaged in discussion.
As severe storms and rising summer highs become more common, tree plantings are buffering neighborhoods in cities like Oklahoma City — reducing energy bills and improving storm resilience.
Volunteers in yellow shirts plant a young tree in Peoria, AZ, with a child assisting and others helping with the digging process.
Amid urban expansion and aging green infrastructure, new canopy plantings are restoring shade in residential zones struggling with high summer temperatures.
A diverse group of volunteers stands in front of a Friends of Trees tent in a park in Portland, OR, surrounded by tall evergreens.
Historic tree loss from storms and development left low-canopy pockets in east Portland, driving local partners to take action and begin replanting.
A group of volunteers planting trees in a green park in Queens, NY, surrounded by lush foliage and dirt tools.
With borough-wide canopy still below the 24% NYC average, new plantings in undercanopied areas are key to delivering relief from the heat.
A street in San Francisco with volunteers planting trees and preparing soil, bordered by residential buildings and parked cars.
Low-canopy districts — especially in the Mission and Bayview-Hunters Point — remain heat-vulnerable; greening projects are strategically targeting heat-susceptible blocks to cool and connect communities.
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What role do trees play in reducing the urban heat island effect?

In cities and towns alike, trees are increasingly recognized as critical infrastructure for survival in increasingly hot summers. In addition to the personal toll, nearly every sector of business is feeling heat stress, from tourism to construction to higher energy bills in offices.

As excessive heat becomes more common and more dangerous, especially in urban areas, trees offer one of the most effective and affordable solutions to protect public health. When planted strategically, trees can:  

  • Cool neighborhoods by up to 10°F, significantly reducing the risk of heat-related illnesses and deaths, especially among vulnerable populations like children, the elderly, and people with preexisting health conditions. Incorporating green spaces along streets and walking paths is also an important way to protect commuters and people who work outdoors.
  • Lower household energy costs by providing shade and reducing the need for air conditioning — a lifeline for low-income households that may struggle to afford rising utility bills. This also reduces the strain on the broader power grid.
  • Filter pollutants that are often exacerbated by high temperatures. This can be especially important for those living with asthma, heart disease, and other health issues through the hotter months.

According to last year’s Canopy Report, the majority of Americans have experienced a natural disaster where they live, with excessive heat leading the way. Planting trees intentionally helps make summers safer. 

How hot is your street? 

This map shows the heat index of cities and towns and the density of tree canopy cover. Enter your city in the search bar in the upper right corner and toggle the map to explore how more trees correlate with cooler temperatures — and see the state of trees and heat on your street. 

When we plant to help cool streets, we start with mapping like this to identify where trees are needed. Then, we work with local partners to plant alongside communities. 

Planting Where It Matters Most

As extreme weather challenges intensify and extreme heat threatens more lives each year, Americans aren’t just calling for action — they’re looking to trees as a proven solution. The science is clear, and the public is aligned: trees have the power to cool our cities, protect public health, and help make communities more resilient. 

That’s why the Arbor Day Foundation is helping cities and neighborhoods fight extreme heat from the ground up. Through an unmatched network of local partners, the Foundation is identifying the most heat-vulnerable, low-canopy areas and planting trees where they’ll have the greatest impact — both today and for generations to come.  

This is more than a planting initiative. With data in hand and committed partners on the ground, the Arbor Day Foundation is working to bring relief — and resilience — to every neighborhood facing the heat.  

You can plant trees where they're needed most

Your gift can bring relief to our cities’ hottest streets by planting trees. It’s the easiest way to protect communities from summer heat.

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Climate Change
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