We’re the mayors of Paris, Milan and Phoenix. The heat crisis has us all facing the same question | Emmanuel Grégoire, Giuseppe Sala and Kate Gallego — Our three cities are learning from each other about how to protect residents. These climate policies are also public health measures
This summer, mayors met in London during the heatwave that ironically threatened to derail London Climate Action Week.
As temperatures broke records across the UK and Europe, leading some climate talks to be suspended or cancelled, we found ourselves seeking shelter and comparing how our cities prepare for extreme heat: how we protect vulnerable residents, communicate risk, and redesign neighbourhoods for hotter summers.
At the same time, Paris was overseeing the city’s crisis response as another intense heatwave swept across France. Across Europe, more than 14,000 people lost their lives due to the heat.
As mayors, we are confronting the same question: how do you protect millions of people when extreme heat is no longer an exceptional event, but an increasingly familiar part of summer?
For Phoenix, that question has shaped city government for decades. For Paris and Milan, it is now becoming one of the defining challenges of urban leadership.
It may strike some people as unusual that two of Europe’s oldest and most prestigious cities are looking to a city in the Arizona desert for ideas. But rising temperatures are now a global challenge, and we don’t have time for each city to figure out what works on its own.
Phoenix has learned, sometimes the hard way, that extreme heat cannot be treated as simply a weather event. It shapes decisions about transport, housing, public health, public space, and emergency planning. Preparing for summer begins long before temperatures start to rise.
Phoenix established one of the world’s first city offices dedicated to heat response and mitigation, reflecting an approach that focuses on both immediate relief from extreme heat, especially for those most vulnerable, and building resilience in the medium-long-term by implementing cooling solutions to make the city safer and more comfortable.
The city’s shade plans require 75% shade coverage in new development in areas with high pedestrian activity, and programs that support schools, transit users, and those most vulnerable. To further reduce the urban heat island effect, Phoenix is applying cool surface treatment to buildings and roadways, including on more than 300 kilometers of neighborhood streets.
The city leads its region in heat response, including providing a 24-hour cooling center with wraparound support to connect people with resources such as housing, medical services, and even job placement. Landlords are required by law to maintain a safe indoor temperature (28C/82F or lower), and companies that contract with the city must implement heat safety plans to keep workers healthy and comfortable. These measures save lives: during the summer of 2024, which was the hottest on record in Phoenix, the city’s coordinated heat response measures contributed to a 20% year-over-year decline in heat-related 911 calls.
Paris and Milan bring different expertise as well as unique challenges.
Both are historic European cities where streets, buildings and public spaces were designed for a different time and a different climate. Today, both cities are adapting.
Every Parisian now lives within a seven-minute walk of a cool spot. The city now has more than 1,400 of these spaces where people can cool down during a heatwave, including parks, gardens and other public facilities. The city also extends opening hours for parks, swimming pools, and public baths during high temperatures. The city has mobilised a network of 27,000 climate volunteers to raise awareness within their communities of the climate crisis and heatwave adaptation strategies, alongside preventive actions.
The city is also planning for a future that would have been inconceivable to Parisians just a few decades ago: “Paris at 50°C” was organised in October 2023 to test the responsiveness of the municipality and its partners, as well as improve planning and coordination for future heat emergency responses. This involved the whole community, utilities, media and schools and directly inspired Barcelona to carry out the same exercise in 2027.