A new global coalition of cities has pledged urgent, coordinated action to address one of the most dangerous impacts of the climate crisis – extreme heat.
Announced during the first day of the C40 World Mayors Summit in Rio de Janeiro, the Cool Cities Accelerator aims to help urban leaders protect residents, safeguard economies, and redesign cities for a hotter future.
The initiative brings together 33 founding cities, representing more than 145 million people worldwide — including five African cities: Accra (Ghana), Durban (Ethekwini) and Tshwane (South Africa), Freetown (Sierra Leone), and Nairobi (Kenya).
C40 established the Accelerator with support from The Rockefeller Foundation, alongside implementation partners such as the ClimateWorks Foundation, Robert Wood Johnson Foundation, Z Zurich Foundation, Danish Ministry of Foreign Affairs, and IBM.
Extreme heat is already the deadliest weather-related hazard globally, responsible for nearly half a million deaths each year. Without decisive action, the number of people exposed to life-threatening urban heat could increase fivefold by 2050.
The Cool Cities Accelerator offers a science-based, practical framework for cities to take both immediate and long-term action. Participating cities will collaborate, share best practices, and issue progress reports focused on:
Protecting residents now by strengthening early warning systems and ensuring access to cooling during emergencies within two years.
Transforming cities for the future by improving building standards, expanding urban tree cover and shade, and future-proofing critical infrastructure within five years.
“Extreme heat is no longer a distant threat — it’s a daily reality affecting the lives and livelihoods of millions around the world,” said Elizabeth Yee, Executive Vice President of The Rockefeller Foundation. “Through the Cool Cities Accelerator, we’re proud to support mayors who are investing in bold, science-based solutions to future-proof health systems.”
C40 Cities Executive Director Mark Watts added: “Extreme heat is a silent killer and an increasingly urgent global threat. The number of days that major capitals experience temperatures above 35°C has increased 54% over the past twenty years. Cities are showing real leadership by taking practical steps to protect communities, safeguard economies, and create more liveable urban environments.”
In support of the initiative, The Rockefeller Foundation is providing a grant of approximately USD 1 million to develop heat adaptation targets and provide technical assistance to cities implementing mitigation solutions.
The Cool Cities Accelerator forms part of C40 Cities’ broader mission to promote bold, science-based climate action across the world’s most influential urban areas. By sharing strategies and scaling proven solutions, cities like Nairobi are joining a global movement to save lives, strengthen resilience, and build cooler, safer cities for generations to come.
