Eric Mackres is senior manager of urban analytics for the WRI Ross Center for Sustainable Cities and attended London Climate Action Week during the June 2026 heatwave.Usama Bilal is an associate professor of epidemiology and co-director of the Urban Health Collaborative at Drexel University.
As thousands gathered in London for one of the year’s largest climate gatherings last week, Western Europe faced its most severe heatwave ever recorded. The irony was not lost.
Across Europe, over a dozen countries issued urgent heat warnings and Spain registered significant deaths. In London, where air conditioning is rare in buildings and on trains and buses, temperatures soared past 36 degrees Celsius (97F) and schools closed early. The mayor announced the city’s first heat action plan - an important step.
Extreme heat is now a public health crisis for many of the world’s cities, as the urban heat island effect intensifies dangerous temperatures - and it’s growing worse. Around 500,000 people die from extreme heat every year. As global temperatures rise, and with a severe El Niño getting underway, even more people will die and be hospitalised unless cities act soon.
But most cities are still taking a far too one-sized-fits-all approach to tackling heat, looking only at temperatures and not its local effects on people and their health.
Eric Mackres is senior manager of urban analytics for the WRI Ross Center for Sustainable Cities and attended London Climate Action Week during the June 2026 heatwave.Usama Bilal is an associate professor of epidemiology and co-director of the Urban Health Collaborative at Drexel University.
As thousands gathered in London for one of the year’s largest climate gatherings last week, Western Europe faced its most severe heatwave ever recorded. The irony was not lost.
Across Europe, over a dozen countries issued urgent heat warnings and Spain registered significant deaths. In London, where air conditioning is rare in buildings and on trains and buses, temperatures soared past 36 degrees Celsius (97F) and schools closed early. The mayor announced the city’s first heat action plan - an important step.
Extreme heat is now a public health crisis for many of the world’s cities, as the urban heat island effect intensifies dangerous temperatures - and it’s growing worse. Around 500,000 people die from extreme heat every year. As global temperatures rise, and with a severe El Niño getting underway, even more people will die and be hospitalised unless cities act soon.
But most cities are still taking a far too one-sized-fits-all approach to tackling heat, looking only at temperatures and not its local effects on people and their health.
People experience heat differently
How extreme heat affects people’s health can vary widely across a country and city, depending on their environment and demographics. Cities can save far more lives and prevent more hospitalisations by taking a tailored approach, using data to understand who’s most vulnerable and directing solutions toward them.
The good news: better data now exists that enable cities to pinpoint who’s most at risk. And that data can inform customised adaptation strategies to save lives. Indeed, the future of cities will hinge on their ability to deliver solutions to extreme heat tailored to at-risk people and neighborhoods.
First, cities should start by measuring heat’s risks to people’s health locally. Our work in Brazil and across Latin America shows big differences in what temperatures are dangerous and how quickly risks escalate at higher temperatures. These variations exist between cities, between demographic groups and between neighbourhoods.
But it’s not as simple as finding the hottest places. In temperate Porto Alegre, in southern Brazil, a person’s risk of death increases by 25% at temperatures of 27 degrees Celsius (81F). In tropical Teresina, in northern Brazil, which is hot year-round, the same temperature does not elevate the risk of death. At 32 degrees Celsius (90F), a person’s risk of death increases by a milder 10%.
These differences also exist within cities where the climate is the same. Elderly people, the very young, lower-income communities and those without air-conditioning and shaded green spaces are all more likely to get sick, be hospitalised, or die from heat. Areas with more trees and green spaces usually have lower temperatures, and therefore lower impacts of heat.
Targeted heat alerts
Second, cities can use this data to develop early warning systems and outreach campaigns that give people more targeted heat alerts. Research in the UK found that the elderly, despite being among the most at-risk, often were unable to heed warnings during the 2022 heatwave. Well-designed heat warning systems and city responses strengthen people’s trust in health services. They can change people’s behaviours and better prepare municipal services, helping reduce illness, hospital visits and deaths.
Rio de Janeiro adopted a heat alert system in 2024 with five alert levels based on past heatwaves’ impacts on health and forecasts of when temperature and humidity will hit those dangerous levels again. The alert levels activate services like cooling centres, extra public drinking water, and changes to outdoor events. When a heatwave struck during Carnival in 2025, the city was able to deploy resources to protect and warn people while still allowing events to go on.
Finally, cities should use local heat data to target cooling solutions to where they can help people the most. Solutions like tree cover, shade structures and cool roofs lower temperatures and can provide targeted relief for the most vulnerable people, like outdoor workers and those who travel by foot, bike or public transit.
In Florianópolis, Brazil, we helped the local government use heat impact modeling to design a green corridor and urban forestry project that will reduce pedestrians’ heat stress up to 7 degrees C. In Hermosillo, Mexico, our researchers worked with the city and found that certain neighbourhoods could feel up to 14 degrees C hotter than the shaded city center. A park is now under construction that will bring better shade and heat relief to one of the city’s most at-risk areas.
Connecting health and climate planning
Momentum to address extreme heat in cities is growing, from both national and local governments. At last year’s UN climate summit in Brazil, the Belém Health Action Plan saw 30 national health ministries commit to build climate-resilient health systems based on local data and evidence-based policies.
And over 160 local governments joined the Beat the Heat initiative, committing to develop urban heat action plans and deliver passive cooling projects to reduce health risks.
But there’s still a disconnect between health, urban and climate officials. Only 23% of World Meteorological Organization member countries integrate weather information into health surveillance systems. Heat-health impact models, though increasingly easy to scale, are not yet built for every city. Some cities still need to collect local data for specific demographics and neighbourhoods - and many need support.
National and local governments will need to partner on this tailored approach. It will require integrating local heat and health data into public health systems, city planning, infrastructure, and disaster preparedness.
We have the data to know who will be most impacted by extreme heat when - and the solutions to keep people alive and out of the hospital. It’s time for governments to use them.
Our unprecedented reporting provides experts and professionals globally with the analysis and insight they need to navigate the most important climate issues.
Trusted by the UN, World Bank, and governments around the world, sign up today and see why our award-winning coverage has been considered the authority for almost 15 years.
Essential
£0
A few top stories each week alongside our Climate Weekly newsletter.
With promises to lift a ban on oil and gas exploration and scale back renewables support, Colombia’s new Tiger President could threaten the country’s clean energy shift
By reviving the problematic industry in the name of energy security, China runs the risk of higher emissions, stranded assets and setting back its ambitions as a clean energy leader
Consultations are underway on reforms to streamline the talks, which take too long to produce outcomes that are often not adequate to tackle the scale of the climate crisis
At this month’s Our Ocean Conference in Mombasa, campaigners warned that ocean protection requires governments to halt new offshore fossil fuel projects
A group of dozens of countries seeks to build momentum for a COP31 pledge to electrify 35% of global energy use by 2035 as an alternative to fossil fuels
With promises to lift a ban on oil and gas exploration and scale back renewables support, Colombia’s new Tiger President could threaten the country’s clean energy shift
This event is co-hosted by the Business and Human Rights Resource Centre, Chatham House, Climate Home News and the Natural Resource Governance Institute.
15 years covering the climate decisions that matter.
Create a free account to join the community of readers — diplomats, negotiators, and campaigners — who rely on Climate Home News.
To provide the best experiences, we use technologies like cookies to store and/or access device information. Consenting to these technologies will allow us to process data such as browsing behavior or unique IDs on this site. Not consenting or withdrawing consent, may adversely affect certain features and functions.
Functional
Always active
The technical storage or access is strictly necessary for the legitimate purpose of enabling the use of a specific service explicitly requested by the subscriber or user, or for the sole purpose of carrying out the transmission of a communication over an electronic communications network.
Preferences
The technical storage or access is necessary for the legitimate purpose of storing preferences that are not requested by the subscriber or user.
Statistics
The technical storage or access that is used exclusively for statistical purposes.The technical storage or access that is used exclusively for anonymous statistical purposes. Without a subpoena, voluntary compliance on the part of your Internet Service Provider, or additional records from a third party, information stored or retrieved for this purpose alone cannot usually be used to identify you.
Marketing
The technical storage or access is required to create user profiles to send advertising, or to track the user on a website or across several websites for similar marketing purposes.