Global coalition of 33 cities launches Cool Cities Accelerator to fight extreme heat and redesign urban spaces

Announced on the opening day of the C40 World Mayors Summit in Rio de Janeiro, the Cool Cities Accelerator aims to protect residents, safeguard economies, and transform urban environments to withstand rising temperatures. The initiative, supported by The Rockefeller Foundation, brings together cities representing more than 145 million people — including Austin, Boston, Buenos Aires, Freetown, London, Nairobi, Phoenix, Paris, and Singapore — united by a shared goal: to make their cities cooler, greener, and more resilient by 2030.

A global response to a deadly climate threat

Extreme heat is now the deadliest weather-related hazard worldwide, responsible for nearly 500,000 deaths annually. Without urgent action, the number of people exposed to life-threatening urban heat could increase fivefold by 2050. According to C40, most heat-related deaths are preventable through timely interventions such as access to cooling centers, clean water, medical assistance, and improved urban design.

The Cool Cities Accelerator, developed by C40 Cities with implementation support from the ClimateWorks Foundation, Robert Wood Johnson Foundation, Z Zurich Foundation, and the Danish Ministry of Foreign Affairs, offers a science-based framework to guide local governments in short- and long-term adaptation measures.

Action plan: from immediate protection to long-term transformation

Participating cities have committed to two main goals:

• Protecting residents now: establishing heat leadership structures, expanding early warning systems, and ensuring access to cooling shelters and emergency resources within the next two years.

• Transforming cities for the future: implementing stricter building standards, expanding urban tree cover and shaded areas, and reinforcing critical infrastructure within five years.

This initiative aligns with the United Nations Secretary-General’s call to action on extreme heat and supports the COP30 Beat the Heat agenda, a global campaign to accelerate local adaptation and promote sustainable cooling solutions.

Leadership and collaboration across continents

C40 has already been supporting cities such as Accra, Austin, Bengaluru, Durban, Freetown, Jakarta, London, Milan, Nairobi, New York City, Quezon City, Rio de Janeiro, and Tshwane, providing technical assistance to enhance their heat resilience.

Haris Doukas, Mayor of Athens, highlighted how the Greek capital is already taking ambitious steps:

“Athens is one of Europe’s most heat-affected cities. Through our heat governance system, including the appointment of a Chief Heat Officer, new green spaces, micro-forests, and cool shelters, we are redesigning the city to protect our most vulnerable citizens. Over the next five years, we will continue to make Athens cooler, greener, and safer.”

Elizabeth Yee, Executive Vice President of The Rockefeller Foundation, emphasized the urgency of local leadership:

“Extreme heat is no longer a distant threat — it’s a daily reality. Through the Cool Cities Accelerator, we’re supporting mayors who are implementing science-driven strategies to protect health systems, strengthen economies, and redesign urban life for a safer future.”

Mark Watts, Executive Director of C40 Cities, noted that the frequency of dangerously hot days has risen sharply:

“Major capitals are now facing 54% more days above 35°C than twenty years ago. Cities are showing true climate leadership by taking decisive, practical steps to protect communities and economies.”

Jessica Brown, Senior Director for Adaptation & Resilience at ClimateWorks Foundation, added:

“We’ve mobilized $50 million in resilience funding to help vulnerable communities adapt to heat risks. Through this initiative, local organizations can drive meaningful change and chart a more resilient path forward.”

Building cities for a hotter world

The Rockefeller Foundation is providing an initial $1 million grant to establish measurable adaptation targets and deliver technical support to participating cities.

The Cool Cities Accelerator is part of C40’s broader mission to scale up science-based climate action across the world’s largest urban centers. By sharing proven strategies and coordinating resources, the coalition aims to help cities act faster and more effectively against escalating heat threats.

Together, the 33 participating cities are shaping a global movement to save lives, strengthen urban resilience, and build thriving, heat-resilient communities for generations to come.