Nairobi among 33 cities picked to fight extreme heat

A new global coalition of cities has pledged urgent, coordinated action to tackle one of the most dangerous impacts of the climate crisis - extreme heat.

Announced on the first day of the network of nearly 100 mayors of the world’s leading cities - the C40 World Mayors Summit in Rio de Janeiro on Monday, the Cool Cities Accelerator programme will help urban leaders protect residents, safeguard economies and redesign cities for a hotter future.

The summit, which ended yesterday, brought together mayors from nearly 100 C40 cities, alongside business leaders, philanthropists, investors, academics and civil society. 

The initiative brings together 33 founding cities representing over 145 million people from every region of the world. The coalition includes five cities in Africa, namely Accra (Ghana), Durban (Ethekwini) in South Africa, Freetown (Sierra Leone), Nairobi and Tshwane in South Africa.

The C40 established the Accelerator with support from The Rockefeller Foundation, and with implementation support from ClimateWorks Foundation, Robert Wood Johnson Foundation, Zurich Foundation, Danish Ministry of Foreign Affairs and IBM.

Extreme heat is already the deadliest weather-related hazard worldwide, responsible for nearly half a million deaths each year.

Without decisive action, the number of people exposed to life-threatening urban heat is projected to increase fivefold by 2050. These 33 cities are committed to taking that decisive action.

The vast majority of deaths caused by extreme heat are preventable through timely access to cooling, hydration, medical care, public health interventions, and improved infrastructure.

These preventable deaths typically occur when individuals—especially vulnerable populations such as the elderly, outdoor workers, or those without access to air conditioning—are not adequately protected during periods of dangerously high temperatures.

Failure of cities to act to reduce heat in their environments has created what is called an urban heat island (UHI).

A UHI is a metropolitan area that is significantly warmer than its surrounding rural areas due to human activities and urban construction.

This phenomenon is caused by materials like asphalt and concrete absorbing and storing heat, a lack of vegetation that provides shade and cooling, and waste heat from human activities such as cars and air conditioning.

A UHIs can negatively impact public health, increase energy costs and worsen air quality.  The Cool Cities Accelerator provides 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 on:

Protecting residents now by establishing clear heat leadership, 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 the Executive Vice President of The Rockefeller Foundation Elizabeth Yee.

“Through the Cool Cities Accelerator, we’re proud to support mayors who are investing in bold, science-based solutions to future-proof health systems, ensuring they can withstand 21st-century challenges. Local leaders are not just responding to the climate crisis today—they’re redesigning urban life to protect people, strengthen economies, and build a cooler, safer future for all.”

Mark Watts, Executive Director of C40 Cities, said extreme heat has become a global threat and something needs to be done urgently about it. “Extreme heat is a silent killer and an increasingly urgent global threat,” said Watts.

“The number of days that major capitals experience temperatures above 35°C has increased by 54 per cent 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 Cool Cities Accelerator, The Rockefeller Foundation is providing a grant of approximately $1 million (Sh129 million) to develop targets for heat adaptation and provide technical assistance to cities to implement solutions that mitigate the dangerous effects of extreme heat.

The Cool Cities Accelerator is part of C40 Cities’ broader mission to support bold, science-based climate action in the world’s largest and most influential urban areas. By sharing strategies and scaling proven solutions, cities can act faster and more effectively than they could alone.

Together, participating cities represent a global movement to save lives, strengthen resilience, and create thriving, heat-resilient cities for generations to come. Other cities that are part of the Cool Cities Accelerator include Ahmedabad, Amsterdam, Athens, Austin, Barcelona, Bengaluru, Boston, Buenos Aires, Chicago, Fortaleza, Guadalajara, Karachi and London.

Melbourne, Milan, Mumbai, New York City, Paris, Phoenix, Quezon City, Rio de Janeiro, Rome, Salvador, Santiago, Singapore, Tel Aviv–Yafo, Tokyo and Vancouver are also part of the programme.