Most Cities Are Getting Hotter. Not All Residents Feel It Equally
On a hot day in February 2024, volunteers dispersed across Cape Town, South Africa, with sensors affixed to their cars. Their aim was to measure heat differences across the city. In Cape Town's dense, highly developed center, they recorded air temperatures as high as 41.6 degrees C (106.9 degrees F). Informal settlements like Joe Slovo, just north of the city center, were nearly as hot. Yet, leafier residential areas southeast of downtown barely broke 25 degrees C (77 degrees F).
In the world’s largest capitals, the number of extremely hot days (above 35 degrees C, or 95 degrees F) per year has risen 25% since the 1990s. Within cities, heat is felt unevenly across communities — but some cities are finding ways to fix that.
The Inequity of Heat
Urban residents who are already socially and economically vulnerable face the greatest risks from extreme urban heat, according to the Intergovernmental Panel on Climate Change. In Mumbai, where temperatures can surpass 38 degrees C (102 degrees F), the whole city can feel sweltering and all residents are at risk of heatstroke. But WRI India research has found that lower-income wards are up to 5.5 degrees C (10 degrees F) hotter than wealthier areas, magnifying already-hazardous conditions.
At the core of this disparity is the composition of the urban landscape. More well-resourced areas tend to have more vegetation, trees and buildings made of heat-resistant materials — all of which help protect residents from extreme temperatures. Lower-income areas and informal settlements, by contrast, often have less greenery and more buildings made of cheaper, heat-trapping materials like metal, making high temperatures even more unbearable.
But socioeconomic disparities explain only part of the variation in how people experience heat across a city. As in Cape Town, central districts with dense development and busy pedestrian corridors often lack the vegetation and shade needed to keep cool. In major tourist areas, like the President’s Mansion (Casa Rosada) in Buenos Aires or Mexico City’s Zócalo, people often gather in open, unsheltered plazas that trap heat, exposing large numbers of people to potentially dangerous temperatures. As more cities around the world commit to mitigating extreme heat — over 200 cities have joined the UN’s Beat the Heat initiative to accelerate local action — it’s vital that decision-makers recognize an important truth: While there is no one-size-fits-all solution for urban heat, there are cooling solutions that can work across a range of different cities and contexts.
A good starting point is better data that shows just how widely heat hazards vary across cities, neighborhoods and even streets. WRI’s Cool Cities Lab data platform enables hyperlocal heat-risk analysis and scenario modeling of different cooling solutions. Here, we explore how three cities around the world experience heat inequity — and how they’re using locally appropriate solutions to alleviate it.
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Cool Cities Lab delivers local heat data directly to cities. Explore where heat risks are most acute, and visualize how these hot spots overlay with vulnerable populations and infrastructure. Estimate the impacts of cooling solutions ranging from street trees to cool roofs. Learn more about Cool Cities Lab.
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Cape Town, South Africa: Cooling the Neighborhoods that Need It Most
Cape Town is clear-eyed about its future on a warming planet. By 2050, the city could experience over 20 more high-heat days (equal to or more than 35 degrees C or 95 degrees F) and up to 10 more heatwaves each year than today, if global temperatures rise by 1 to 3 degrees C (1.8 to 5.4 degrees F), according to the city’s Chief Heat Officer Albert Ferreira. Prolonged exposure to extreme heat can worsen health problems like dehydration, heatstroke and heart disease. Higher temperatures could also strain the city’s infrastructure by damaging roads, overloading electrical grids and ramping up demand for cooling.
Yet heat is not felt equally throughout the city. Decades of race-based exclusion in housing has concentrated lower-income people of color in many of Cape Town’s poorest, most densely built neighborhoods. Houses there are often made of corrugated metal or plastic, which trap heat. Limited vegetation and shade throughout these neighborhoods leave residents with almost nowhere to escape from the heat. For communities like Atlantis, Mamre, Dunoon, Joe Slovo and Sir Lowry’s Pass Village, the future of regular 35 degrees C (95 degrees F) days is already a reality.
Recognizing these neighborhood-level differences is helping Cape Town target heat solutions more effectively. Through Cool Cities Lab data — including maps of neighborhood heat exposure and estimates of the cooling potential of trees, reflective roofs and other solutions — city officials can see where interventions could have the greatest impact. “With access to this data, we can clearly identify vulnerable areas and quantify the potential temperature reductions from different solutions,” Ferreira said.
These insights can help secure funding for heat-resilient infrastructure and improve communication between city leaders and residents of vulnerable communities about how heat solutions can help them. It also highlights the advantage of short-term solutions that can provide immediate relief. Urban heat planning often focuses on greening and nature-based solutions, like new parks, as one of the most effective ways to reduce temperatures. Yet these benefits can take time to materialize. Trees, for example, can take years to grow enough to provide shade. Cape Town is using Cool Cities Lab data to complement these long-term greening efforts with quick-win interventions that can provide cooling relief quickly.
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In Khayelitsha, one of Cape Town’s poorest areas, the city is working with residents through the Heat Adaptation Benefits for Vulnerable groups in Africa project to roll out reflective roof paint across homes to demonstrate its cooling potential. Studies have shown that cool roofs can lower indoor temperatures by 1.5 to 5 degrees C (2.9 to 9 degrees F) and reduce surrounding air temperatures by 0.2 to 0.6 degrees C (0.4 to 1.1 degrees F) for every 10% increase in neighborhood reflectivity. Ferreira sees it as a first step, with shaded areas, cooling centers and urban greenery in vulnerable communities to follow. “These efforts can reduce compounding climate and social stressors in communities through improving health conditions and public spaces,” he said.
Hermosillo, Mexico: Greening a Desert City
In late July 2025, residents of Hermosillo baked under record-high temperatures of 46 degrees C (114.8 degrees F). The “city of sun” is no stranger to heat. But under these intense conditions, daily life became difficult. Outdoor workers started their day before sunrise to avoid the worst of the heat. Commuters pressed damp towels to their heads and necks to cool off.
But conditions varied considerably. In the city center, where mesquite trees cover public plazas and buildings, people were able to find some respite in the shade. In peripheral neighborhoods, few trees and poorly ventilated buildings trapped the heat. Residents struggled to sleep and reported headaches, dizziness and dehydration as they moved through the city.
Hermosillo has long experienced extreme heat — and will continue to as climate change is expected to raise temperatures in northern Mexico by 4 degrees C (7.2 degrees F) by the end of the century. Longtime residents recall a time when the city was more equipped to handle it, with more vegetation that provided relief from the heat. In recent decades, the region has shifted from an economy built around livestock and agriculture into a thriving urban center, replacing large swaths of vegetation with roads, housing and concrete. At the same time, water scarcity from urban growth and increasing droughts has led to the removal of trees along major boulevards and in public spaces to conserve resources.
Hermosillo city officials are using data from WRI’s Cool Cities Lab to understand how these changes have shaped the city’s heat exposure. By mapping neighborhood-level heat patterns, they've identified where vegetation loss and increased concrete have intensified temperatures. Officials refer to these vulnerable areas as “red zones,” said Jose E. Carrillo, general director of the Hermosillo Municipal Institute of Urban Planning. “It’s a big help to be able to show people these differences visually on a map and show them why we need to take action in the city.”
The data showed that the northwest portion of the city has the lowest rate of vegetation cover (just 0% to 6%) and can feel up to 14 degrees C (25.2 degrees F) hotter than the cooler areas of the city — a difference significant enough to increase mental and physical health risks for residents. In response, Hermosillo began construction on a new urban park, Cárcamo Norte, in early 2026 to provide residents with more green space and relief from the heat. In other areas where heat risk appears particularly acute — especially newer, more peripheral neighborhoods with little vegetation -- the city is working to add greenery and trees for shade.
Hermosillo recently established a native plant nursery to seed efforts to restore trees and plants. With neighborhood-level data guiding these efforts, city leaders can identify where restoring vegetation will have the greatest impact. The city is also using data to identify where cooling shelters and additional shade from trees and structures could benefit people along major transit and pedestrian routes.
Atlanta, Georgia: Cooling a City with Cool Roofs
When the sun beats down in Atlanta, residents of the Westside feel it the most. These predominately Black communities can experience temperatures up to 5.6 to 8.4 degrees C (10 to 15 degrees F) hotter than other parts of the city. Residents suffer more from heat stress and related health risks.
The difference in temperature is rooted in the legacy of century-old racist housing policies. In the 1930s, neighborhoods in Atlanta’s Westside were labeled as “hazardous” by federal housing authorities. Residents were denied access to affordable mortgage rates in a process known as redlining. This designation led to decades of structural underinvestment that can still be felt today.
“The areas that have this history of redlining are often the hottest,” Evan Mallen, a Georgia Tech climate researcher who co-led a study on climate vulnerability in Atlanta, told Capital B News. “They’ve got the lowest tree canopy and the highest asphalt, concrete, impervious surface coverage, which contributes to urban heat.”
The built environment in these neighborhoods traps heat and raises health risks like heatstroke and heart disease. At the same time, many residents lack air conditioning due to aging housing and high costs. While 96% of residents elsewhere in Atlanta have air conditioning in their homes, less than 80% of Westside residents do — leaving the city’s most vulnerable residents few options to cool down.
To better understand where these risks are most concentrated, Atlanta commissioned the 2023 Georgia Tech study to map heat vulnerability across the city, which found stark disparities among neighborhoods. The city worked with the Smart Surfaces Coalition (SSC) — an organization that supports uptake of urban cooling solutions — to identify the most effective cooling strategies.
Their modeling analysis, developed in partnership with WRI using data now available in Cool Cities Lab, showed that upgrading roofs with reflective materials could lower citywide air temperatures by around 1.4 degrees C (2.4 degrees F) — a reduction large enough to lower both energy demands and instances of heat-related illnesses. In historically redlined neighborhoods, the effect would be even greater, lowering temperatures by as much as 3.5 degrees C (6.3 degrees F). These findings led the city council to unanimously pass an ordinance in June 2025 mandating that all new and replacement roofs must be built with reflective, or “cool,” materials beginning in 2026.
“Cool roofs are a critical strategy for mitigating the urban heat island effect more broadly. Lower temperatures across Atlanta will help protect outdoor workers and pedestrians, reduce citywide energy consumption and peak electricity demand, and improve public health by reducing ozone and other air pollutants,” said Jacob Miller, deputy director of U.S. Policy and Programs at SSC. “Our modeling indicates that the cool roof ordinance could result in more than $300 million in total energy savings over the next 35 years, and mitigate 1,000 metric tons of air pollutants.”
Cooling Cities Equitably
The experiences of Cape Town, Hermosillo and Atlanta show how cities can tackle the drivers of unequal heat exposure. By using detailed data and understanding the needs of residents, city leaders can identify the neighborhoods most at risk and prioritize solutions where they will have the greatest impact. With extreme heat already contributing to an estimated 489,000 deaths each year — and only expected to become more severe — cities need to be investing now in solutions like trees, cool roofs and shade that can lower temperatures in the places where residents feel them the most.
How individuals experience temperatures is shaped by many factors within cities’ control. By acting now, cities can keep their residents safe and build a more resilient future for all.
Learn more about the Cool Cities Lab and explore the data.
Produced by WRI Ross Center for Sustainable Cities
WRI Ross Center for Sustainable Cities is WRI’s program dedicated to shaping a future where cities work better for everyone. Together with partners around the world, we help create resilient, inclusive, low-carbon places that are better for people and the planet.