Extreme heat is a public health emergency. Cities have solutions.

Extreme heat is one of the deadliest and most unequal consequences of climate change. Heatwaves are arriving earlier, lasting longer, and becoming more intense, placing growing pressure on residents, public services and health systems.

Much of the urban infrastructure we engage with today—buildings, roads, and parks, for example—was built for climates experienced in previous centuries. They absorb, retain, and emit heat, often making cities hotter than their surroundings. Outdated infrastructure coupled with the global failure to mitigate rising temperatures means extreme heat is now routinely threatening people’s lives. Exposure to deadly urban heat has tripled since the 1980s.

Exposure is also deeply unequal. Neighborhoods with fewer trees and green spaces, poorer-quality housing, and limited access to cooling can experience the highest temperatures. Older adults, children, outdoor workers, and people with chronic health conditions are less able to protect themselves. When these inequalities overlap, the result can be catastrophic.

Heat stress is the leading cause of death. Rising rates of noncommunicable diseases (NCDs)—like heart disease, diabetes and chronic respiratory disease— are increasing vulnerability and adding pressure to already strained health systems.  Between 2000 and 2019, an estimated 489,000 deaths worldwide each year were associated with heat, with 45% occurring in Asia and 36% in Europe.

But heat-related illness and death can be prevented.

In 2025, the Partnership expanded its work to support cities to strengthen preparedness and reduce the health impacts of extreme heat. With our support, cities are developing heat emergency plans, conducting heat-health impact assessments, and implementing strategies to reduce urban heat, like adding reflective surfaces, shade, trees, and green spaces.

Effective action begins with understanding that heat risk is local. Even within the same city, temperature—and who is most exposed—can vary dramatically from one neighborhood to another.

That makes local data essential. By combining temperature, climate, health and socioeconomic information, cities can pinpoint where heat is most severe, who faces the greatest risk, and where interventions can have the greatest impact.

In Fortaleza, Brazil, for example, the city’s Climate Risk Observatory is strengthening heat surveillance to identify urban heat islands, map areas of risk, and support evidence-based planning. Seoul, South Korea, is analyzing trends in heat-related illness and death, the effects of urban heat islands, and the effectiveness of existing policies. Barcelona, Spain, is evaluating how climate change affects residents’ health, with a focus on ensuring environmental health policies benefit the people who need them most.

The principle is straightforward: once cities know where the risk is, they can act with precision.

Knowing who is vulnerable—and being able to reach them—is one of the most important components of an effective heat response. Cities need to know where older people living alone are concentrated, which homes lack adequate cooling, where outdoor workers face prolonged exposure and which neighborhoods experience both high temperatures and existing health and socioeconomic disadvantage.

This information can support a more targeted response. New York City, for example, is examining energy insecurity among residents at increased risk of heat. Having an air conditioner does not necessarily mean someone can afford to use it throughout a heatwave. Understanding barriers to cooling can help cities develop policies that reflect the realities residents face, rather than offering generic solutions that don’t meet their needs.

Heat protections must also account for people who cannot easily avoid exposure. Outdoor workers may understand that conditions are dangerous but may be unable to stop working without losing income. This is why heat is both a climate and an equity issue: those with the fewest resources to protect themselves can face some of the greatest risks.

Cities have a growing range of interventions available: from early warning systems and cooling centers to shade, reflective surfaces, energy assistance, health-system preparedness and protections for outdoor workers. But adopting an intervention is not the same as making it effective.

Cities need systems that reliably track and forecast heat and humidity and their health impacts at the neighborhood level. They also need clear plans that trigger timely warnings and protective measures, prepare health systems, and coordinate action across city departments.

São Paulo, Brazil, is combining climate and health data with urban, socioeconomic and environmental indicators to design a network of “climate shelters”—public spaces where residents can find relief during periods of extreme heat. Along with Fortaleza and Rio, Brazilian cities are contributing to a growing body of experience that other cities can draw on.

High temperatures are a familiar occurrence in Asia, but the frequency and severity of heatwaves has made it a modern crisis.

In response, Ahmedabad, India, will advance ward-level hotspot mapping, vulnerability assessments, standardized reporting and interdepartmental coordination to strengthen implementation of its Heat Action Plan.

Quezon City, Philippines, for example, will develop health-based strategies, targeted community interventions, early warning systems and response mechanisms. Phnom Penh, Cambodia, will install weather stations across the city to collect the data they need to inform a comprehensive urban heat action plan.

As the world continues to suffer the consequences of climate change, cities are prioritizing solutions to protect their residents. The Partnership is pleased to provide technical and financial assistance to support the solutions that will end up protecting millions of people from exposure to extreme heat.