What it is: A toolkit of design, planning, and community care strategies designed to ameliorate the effects of the urban heat island effect and keep city residents cool and safe through extreme heat events. Urban cooling strategies can include: 

• Safe, appealing alternatives to car transit, like walking, biking, and public transportation, which can help take heat-producing cars off the street and shrink the size of heat-absorbing asphalt roads and parking lots. (Plus: Anytime fossil fuel-powered cars are taken off the road, that’s a win for climate change mitigation and local air quality!)
• Light-colored and reflective coatings applied to roads, roofs, and building facades, which have been effective in reflecting rather than absorbing heat. White roofs can reduce the temperature inside the building by an average of 4-5°F, and black asphalt roads assessed in Los Angeles were shown to be a whopping 23°F cooler after they were coated with a white, highly reflective sealant! (Plus: Cool roofs can reduce energy expenses for building residents. According to NYC CoolRoofs, roofs painted with a light-colored, reflective coating reduce air conditioning costs by 10-30% on hot summer days.) 
• Removing pavement altogether. When dark, heat-absorbing, and impervious asphalt is replaced with permeable pavement, vegetation, and other natural ground cover options, water is able to infiltrate and then evaporate when it gets hot, naturally cooling the atmosphere. Preliminary studies suggest that removing just 10% of a neighborhood’s pavement could lower temperatures by 7°F! De-paving walking and biking paths, playgrounds, parking lots, and vacant lots is an excellent place to start. (Plus: When impermeable pavement is removed and water is able to infiltrate into the ground, groundwater aquifers are replenished and stormwater runoff is reduced. De-pavement efforts can help to regulate the water cycle and buffer the impacts of periods of drought and heavy rains.) 
• Simple shade structures and water features, like fountains, sprinklers, public swimming pools, water spray parks, and misting systems, which can give folks a cool respite at bus stops, on benches, and in public gathering spaces. Water features like sprinklers and misting systems can cool people off instantly as water evaporates from the skin, while bodies of water, like fountains, can lower the local temperature by stimulating the evaporation of water into the atmosphere. 
• Weatherizing buildings by sealing gaps around doors and windows, installing attic and wall insulation, adding simple shading systems or solar window film to block out the sun, replacing appliances, lighting, and temperature control systems with energy-efficient options, etc. Weatherization can help to keep hot air out, minimize solar radiation and internal heat sources, and lower humidity levels, significantly improving thermal comfort for residents. (Plus: Meeting the need for weatherization could create tens of thousands of good jobs and opportunities for workforce development. In 2020 alone, the Weatherization Assistance Program supported 28,000 jobs, and there are still millions of buildings that could benefit from weatherization.) 
• Cooling centers, or public spaces with air conditioning that can provide lifesaving relief for folks who don’t otherwise have air conditioning at home or are experiencing a power outage. Good cooling centers are located in places where people naturally gather, like libraries, and have furniture for people to sit on and recline, activities and facilities for children, toiletries for unhoused folks, cool drinks and snacks, power outlets for folks to charge their devices or use their electricity-dependent medical equipment, etc. Cooling centers should be equipped appropriately so that people, and particularly elders, disabled folks, unhoused folks, and young children, who are generally most vulnerable to extreme heat, can comfortably spend the whole day there. (Plus: Well-equipped cooling centers can serve as community resilience hubs during a wide range of climate-related and non-climate-related disasters alike.) 
• Community care strategies, like neighborhood extreme heat plans, first aid trainings, or basic practices like checking in on neighbors or distributing frozen water bottles to unhoused folks. Community care is an absolutely essential element of keeping folks safe during extreme heat events. When public sociologist Eric Klinenberg was analyzing Chicago’s 1995 extreme heat event, during which over 700 people died, he found that community cohesion, or lack thereof, was the largest predictor of how neighborhoods fared during the heatwave. People were far more likely to survive if they had a close connection to another person.
• Adding plants in all forms, including green walls and roofs, parks, community gardens, green corridors, urban forests, and even potted indoor plants. Plants cool the air temperature by stimulating transpiration, the process by which water vapor is released from plant leaves into the atmosphere. Trees, which also deflect solar radiation and provide shade, are generally the most efficient heat mitigation strategy, particularly when clustered in places where people gather or that they utilize frequently, like in parks, along highly trafficked walking paths and sidewalks, and by buildings. A 2023 study published in peer-reviewed public health journal The Lancet found that doubling the average amount of tree cover in European cities from 15% to 30% could reduce heat-related deaths by more than a third! Other forms of vegetation can have a dramatic impact on lowering temperatures, too; one climate researcher found that walls covered in vining plants had surface temperatures 40°F lower than their bare-walled counterparts next door on extremely hot days, and the temperature on Chicago City Hall’s green roof is approximately 80°F cooler than nearby conventional roofs on a typical day. (Plus: Plants support biodiversity by providing habitat and filtering the air, water, and soil. The presence of plants can meaningfully reduce acute and chronic stress and offer other mental health benefits for folks who live, work, and play in the neighborhood. Green spaces can bolster social cohesion and neighborhood pride. There is even a direct correlation between green surroundings and lower crime rates when controlling for other variables. The list goes on!)

Some additional context: As heat waves become longer, hotter, and more frequent, urban communities experience the impacts most intensely; cities can be up to 22°F hotter than surrounding rural and suburban communities, and they are heating up at twice the rate of non-urban areas. The urban heat island effect results from large swaths of concrete and asphalt, which absorb and radiate the sun’s rays, as well as urban canyons formed between tall buildings that trap heat at the street level. Because heat can’t dissipate well, the urban heat island effect is felt most acutely at night, as temperatures remain high and residents don’t experience a reprieve for their bodies to cool down. The effect is exacerbated by high concentrations of gas-powered vehicles, air conditioning units, and other sources of heat. a

Not every urban neighborhood is affected equally, though. There is tremendous temperature variation within cities, and even within neighborhoods, typically mapping with the racial and socioeconomic history of the region. On average, communities that have been structurally marginalized have significantly fewer trees and green spaces and more parking lots and pavement. In fact, a 2020 study of 108 urban areas across the United States found that formerly redlined neighborhoods of nearly every city studied were notably hotter than nonredlined neighborhoods, sometimes by nearly 20°F. Low-income communities and communities of color are therefore disproportionately impacted by the urban heat island effect. Unfortunately, the disparity in the experience of extreme heat along race and class lines is often exacerbated by lack of access to air conditioning. 

The consequences of extreme heat are serious. When people consistently experience high temperatures without relief, they’re vulnerable to dehydration, heat exhaustion, heatstroke, mental stress, diminished cognitive function, and even death. In the so-called United States, heat waves are responsible for more deaths than any other natural disaster; as many as 12,000 people die from extreme heat each year. Again, not all bodies are affected by extreme heat equally; children, elders, pregnant people, unhoused folks, folks who do physical labor outside, and disabled folks are most vulnerable to the dangers associated with extreme heat. Extreme heat can also exacerbate ozone pollution levels, which can trigger asthma attacks and cardiovascular issues, and sometimes leads to power outages, which can endanger folks who rely on electricity-dependent medical equipment. 

As the climate crisis intensifies, heat waves are bound to become longer, hotter, and more frequent, particularly in cities, where an estimated 83% of the American population resides. Urban cooling projects can and should work on different levels to (1) counter the urban heat island effect, so that cities don’t heat up as much; (2) counter the legacy of racist planning and policy, so that temperature disparities between neighborhoods no longer exist; (3) ensure that urban residents have access to relief even on days when their neighborhood is hot, so that they’re able to cool down and avoid health emergencies; (4) ensure that community members are equipped with training so that they can care for one another when someone is experiencing a heat-related health issue; (5) protect workers from laboring in unsafe conditions, and more. Urban cooling projects are meant to improve comfort and quality of life during extreme heat events as well as prevent acute health emergencies and avoidable deaths, particularly for those most exposed to and/or vulnerable to extreme heat.