As record temperatures swept Europe and the UK this summer, extreme heat response moved to the center of urban leadership. Mayors from Paris, Milan and Phoenix say the escalating crisis raises a shared challenge: how to protect millions when dangerous heat is no longer rare.
During London Climate Action Week, some discussions were suspended or canceled due to the heat, underscoring the urgency. Paris simultaneously managed an intense heatwave at home as soaring temperatures across Europe were linked to more than 14,000 deaths, according to officials. The mayors said cities must treat heat as a cross-cutting risk that shapes transport, housing, public health, public space and emergency planning.
Extreme heat response lessons from Phoenix
Phoenix, long accustomed to brutal summers, has built a model that blends immediate relief with long-term cooling. The city created one of the world’s first municipal offices dedicated to heat response and mitigation, focusing on vulnerable residents while advancing resilience projects.
Key measures include shade requirements that call for 75% coverage in new developments in high-pedestrian areas, support for schools and transit users, and cool surface treatments for buildings and roads. Phoenix has applied such treatments to more than 300 kilometers of neighborhood streets to counter the urban heat island effect.
The city also coordinates regional heat response, operating a 24-hour cooling center with wraparound services that connect people to housing, medical care and job placement. Landlords must maintain indoor temperatures at 28C, or 82F, or lower, and city contractors are required to implement heat safety plans for workers. During the hottest summer on record in 2024, Phoenix reported a 20% year-over-year decline in heat-related 911 calls, which officials attribute in part to these coordinated efforts.
Paris and Milan adapt historic cities for extreme heat response
Paris and Milan are reworking streets, buildings and public spaces designed for cooler eras. In Paris, every resident now lives within a seven-minute walk of a designated cool spot. The city counts more than 1,400 spaces where people can find relief during heatwaves, including parks, gardens and public facilities, and extends hours at parks, pools and public baths when temperatures climb.
Paris has also organized a citywide stress test, “Paris at 50°C,” to evaluate how municipal departments, utilities, media and schools coordinate under extreme conditions, and it has mobilized 27,000 climate volunteers to promote heat adaptation and preventive actions. The exercise inspired Barcelona to plan a similar test in 2027.
Milan is expanding its Piazze Aperte and School Streets programs to integrate cool spaces through tree planting, shaded areas and swapping hard surfaces for permeable green space. The municipality operates Milano Aiuta, a helpline and support service for older adults and other vulnerable residents during heat events. Milan’s Air and Climate Plan sets a binding goal to limit local temperature increases to 2C by 2050, a rare temperature-specific target for a city.
Sharing what works, faster
City leaders caution that no one can copy and paste another city’s blueprint. Geography, history and politics differ. But through networks such as C40 Cities, nearly 100 major cities are trading solutions that can be adapted locally. If one city finds a better way to protect outdoor workers, cool public spaces or communicate risk, others should scale it rather than start from scratch.
Officials note that extreme heat kills more than half a million people each year, making it the deadliest climate hazard. Urban areas trap heat in buildings, roads and pavements, pushing nighttime temperatures higher and reducing relief. Older residents, young children, outdoor workers and lower-income communities face the greatest risks.
From climate policy to public health and jobs
Planting trees, cooling schools, redesigning streets, upgrading buildings and expanding early warning systems are not only climate policies. They are public health measures and investments that make cities more livable, while supporting local economies.
Heating and cooling account for nearly half of Europe’s energy use, with roughly 70% of heating still powered by fossil fuels, according to European data. Cities can lead a fair shift to clean heat by investing in renewable energy and cleaner heating systems, cutting emissions, improving air quality and creating local jobs, with benefits directed to those most in need.
National support is essential
Mayors say cities are often first to feel climate impacts but last to receive the authority, funding and flexibility to respond. They are calling on national governments to co-develop adaptation strategies, expand early warning systems and unlock financing to protect residents. Such investments can save lives, strengthen economies and reduce future costs.
This summer gave Europe a glimpse of conditions familiar to desert cities and a preview of what may become the norm in a warming world. City leaders argue that extreme heat is a collective challenge that requires bold political action. The pace of learning and sharing solutions, they say, must outstrip the speed at which the climate is changing.
For more on the human toll of rising temperatures, see our coverage of how heat-related deaths vastly exceed official counts. Additional data and guidance on heat impacts are available from the World Health Organization.
