London Mayor Sadiq Khan is warning that time is running out to act on the climate emergency, which will have devastating effects on the city.
Mr Khan will say in a speech on Thursday that the capital is at a crossroads.
He will be speaking before key UN climate talks, Cop26, in Glasgow and the expansion of London’s ultra-low emission zone to limit traffic pollution, and as a new environment bill goes through Parliament
Mr Khan will say that the climate emergency remains one of the biggest threats the world faces.
He will launch a London-wide environmental campaign to raise awareness of the crisis.
An analysis suggests that rising temperatures could make the city's Tube unbearably hot for more than a month each year.
A quarter of London’s rail stations are now at high risk of flooding, and this summer parts of the city were hit by flash floods.
Hackney, Hammersmith and Fulham, Islington, Brent, Tower Hamlets and Newham are the boroughs at particularly high risk of flooding and overheating, mapping has shown.
A City of London analysis also shows one in five schools, and nearly half of London’s hospitals, are at risk of flooding, and 200,000 homes and workplaces are at medium or high risk.
According to new World Health Organisation guidelines for limits to air pollution, issued on Wednesday, all children in London attend schools with toxic air, officials said.
“We either take bold action now or face the consequences, with catastrophic impacts on our environment, the air we breathe and the climate," Mr Khan will say in his speech at the Barbican Centre.
“I’m determined for London to be a world leader in tackling the twin dangers of air pollution and the climate emergency so that we can deliver a brighter future for London, one that’s greener, fairer and more prosperous for everyone.”
He has committed to making London a zero-carbon city by 2030, and is expanding the ultra-low emission zone to stop children breathing toxic air.
“But I can’t do it all alone," Mr Khan will say. "That’s why today I’m launching my city-wide campaign to inspire all Londoners – individuals, businesses and communities – to take action.
“I also want to work with the government to unlock the powers and funding needed to meet our targets, which will help to deliver national targets too.”