- New York Mayor Zohran Mamdani and Los Angeles Mayor Karen Bass convene 2026 Urban 20 Summit, with leaders of 35 cities from around the world
- Cities will show how climate action can improve lives by delivering more affordable and resilient homes, cutting energy costs, creating good jobs and protecting communities from extreme weather
- U20 kicks off Climate Week NYC, with C40 mayors advancing action on extreme heat and resilience, responsible data center growth, clean air and sustainable housing
New York, USA (19 September 2026) – Mayor Zohran Mamdani will welcome mayors from across the United States and around the world to New York this weekend, as city leaders unite for practical action on climate, housing, and migration, as well as making communities safer, healthier and more resilient for newcomers and long-term residents.
New York City and Los Angeles are Co-Chairs of the 2026 Urban 20 (U20). The U20 Mayors Summit, taking place from 19–21 September and convened by C40 Cities and United Cities and Local Governments (UCLG), in partnership with the Mayors Migration Council (MMC), is expected to bring together more than 35 cities from across the G20 countries, represented by 25 mayors alongside deputy mayors and senior city leaders.
US cities including Atlanta, Chicago, Denver, Miami, Phoenix, San Diego and Seattle will be represented, alongside cities from across Canada, Europe, Africa, Latin America and Asia. Their presence demonstrates continued US city leadership and the determination of mayors to work across borders and political divides at a moment when international cooperation is under increasing strain.
The summit will focus on three interconnected challenges facing cities and their residents: housing, climate change, and migration.
Mayors will argue that these challenges – alongside the affordability crisis being felt by many city residents around the world – cannot be tackled in isolation. Climate impacts are increasing pressure on household finances and public services, whilst also contributing to driving people from their homes and putting city residents in danger from extreme weather.
Dependence on fossil fuels leaves families and economies exposed to volatile energy costs while contributing to pollution and extreme weather that undermines the health and safety of daily life. At the same time, cities are welcoming newcomers driven by economic opportunity, labour demand, and climate-driven displacement. These are realities that, met well, can strengthen rather than strain local communities.
City leaders will also show how climate action can improve people’s lives now: delivering healthier, more affordable and resilient homes, lowering energy costs, creating good jobs, cleaning up the air, and protecting communities from extreme heat, flooding and other increasingly severe climate impacts.
Mayors will discuss measures cities are already taking to build more affordable housing, protect tenants and make homes and neighborhoods more resilient. On migration, they will examine how cities can welcome newcomers while maintaining strong public services and social cohesion for all residents. Leaders will also focus on accelerating the clean energy transition while ensuring residents benefit through lower costs, greater energy security, good jobs and healthier communities.
Across all three areas, mayors will make the case that cities are ready to deliver, but need the powers, finance and partnerships to match their responsibilities and ambitions.
The summit will conclude on Sunday with the ratification of a communique setting out a shared city agenda for action. Representatives from the United Nations and other international organisations will then be invited to respond.
Cities at Climate Week NYC
The U20 Summit kicks off a major week of city climate leadership in New York, as C40 mayors join leaders from government, business and civil society groups at Climate Week NYC, one of the world’s largest annual gatherings focused on climate action.
Extreme heat and urban resilience will be at the heart of C40’s work throughout the week, with mayors advancing solutions to protect residents as temperatures rise and pushing for greater investment in adaptation and preparedness. The need for these actions has been shown around the world this year, with Europe experiencing record heat and dozens of countries preparing for the impact of the predicted ‘Super El Nino’.
C40 mayors will also advance efforts to create sustainable data centers, building on the principles of the Global Urban Data Centers Pact launched at London Climate Action Week in June. The pact brings together nearly fifty mayors from six continents around a common approach to ensure that the rapid expansion of digital infrastructure supports economic growth without driving up residents’ energy costs or placing unsustainable pressure on electricity grids, water supplies, land, and the environment.
The week will also provide an important staging point towards COP31, where mayors will continue to show that they can work with world leaders to accelerate climate ambition and ensure the experience of cities helps shape the next phase of international co-operation.
Mayor Zohran Mamdani of New York City said: “This weekend, New York City is welcoming mayors from across the United States and around the world, united by a shared belief that the people who keep our cities running should be able to afford to live in them.
“We are proud to co-chair the Urban 20 with Los Angeles and to welcome leaders who refuse to leave working families to face rising rents, soaring energy bills, and deadly heat waves alone, regardless of where they were born or their immigration status.
“At a time of division and retreat, our cities are choosing cooperation and showing what is possible when we work together to build a better future for all.”
Mayor Karen Bass of Los Angeles said: “Cities are on the front lines of the climate crisis, but we are also where solutions are being put into action every day. From building more resilient homes and neighborhoods to creating good jobs, cleaning our air and protecting Angelenos from extreme heat and other climate impacts, we are delivering real results for our communities.
“Los Angeles is proud to co-chair the Urban 20 with New York City to bring US and global mayors together around a shared agenda to make our cities safer, healthier and more affordable.”
Mayor Yvonne Aki-Sawyerr of Freetown, Co-Chair of C40 Cities, and MMC Founding Leadership Board Member, said: “Whether we lead a city in Africa, Europe, Asia or the Americas, mayors from around the world see many of the same pressures on our residents: rising costs, extreme heat, housing insecurity and displacement.
“But cities are also where solutions are being delivered. We want young people to have real opportunities at home, and we want climate change to never be the reason they have to leave. By working together, sharing what works and investing in a just transition, we can tackle the climate crisis while creating jobs, improving lives and making our communities more resilient.
“The message from mayors in New York will be clear: give cities the tools and resources to act, and we will deliver.”
Mayor Ugur Ibrahim Altay of Konya, President of United Cities and Local Governments (UCLG) said: “The spirit we need to carry forward is one of cooperation over division, solidarity over isolation, and shared responsibility for protecting our communities.
“A stronger multilateral system is needed. It will need to trust cities, work with them, and design solutions that can be delivered through them.
“That is the present we are shaping every day and the future we are committed to delivering.
Kate Johnson, C40 Cities Director for North America, said: “At a time when international cooperation is under enormous strain, US mayors joining counterparts from around the world sends an important message: cities are still working together, and they’re focused on getting things done.”
“Mayors understand those connections because they deal with them every day. They are showing that climate action can mean more affordable and resilient homes, lower energy costs, cleaner air, good jobs and communities better protected from extreme weather.”
Emilia Saiz, Secretary General of UCLG, said: ”Public service delivery is about shaping communities in which people can live with dignity.
“That is precisely why the three priorities of this U20 cycle matter: they speak directly to the conditions that shape people’s daily lives and to the capacity of our cities to protect dignity, opportunity and belonging.”
Vittoria Zanuso, Executive Director of the Mayors Migration Council, said: “Affordability, climate and migration are part of the same story: whether people can build stable, dignified lives in the cities they call home.
“By putting migration at the heart of this year’s U20 agenda, mayors are sending a clear message: cities are not waiting for global debates to catch up – They are already delivering solutions and shaping the conversation.
We’re proud to work with Mayor Mamdani, Mayor Bass, C40 and UCLG to carry that leadership forward and back it up with the partnerships and resources needed to scale what works.”
related
Find out more about C40’s announcements and activities at the United Nations General Assembly and Climate Week NYC, taking place in New York City from 20-27 September 2026
C40 mayors and global partners are leading urban climate adaptation and resilience efforts on the front lines.
Cities are shaping the future of the digital infrastructure that powers our digital lives, ensuring data centres are sustainable and benefit local communities.
