London mayor unveils capital’s first heat plan as city swelters under rare red alert

As temperatures in the capital threaten to hit 40°C this week, Sadiq Khan has unveiled London’s first ever heat plan, warning that rising temperatures are “no longer a future threat” but a growing reality reshaping life across the city.

The plan, Heat Ready London, was published today (Thursday 25 June) during London Climate Action Week, with the Met Office issuing only the second red heat-health alert since the warning system was introduced in 2003. Experts say the current spell of extreme heat — combined with high overnight temperatures and humidity — could prove more damaging to health than the July 2022 heatwave.

London is more exposed to heat risk than anywhere else in the UK. Earlier this year the capital recorded an all-time May high of 35.1°C, and the report warns the city could face two to three times as many heatwaves within 20 years as it does now.

The numbers behind the plan are stark. Around one million London homes may currently be at high risk of overheating, alongside 1,361 schools, 60 hospitals and 351 care homes sitting in high-risk areas. A new study found the 2022 heatwaves cost the city an estimated £1.5bn, taking in the combined toll on health, learning, transport, energy use, emergency services, wildfires and lost productivity. That summer also pushed the London Fire Brigade to its busiest day since the Second World War.

Hot weather already brings nearly 4,000 additional hospital attendances across a London summer, on top of an estimated 300 preventable deaths each year in the capital. Wildfires are climbing too: firefighters tackled around 88 across London last June, July and August, with 122 incidents logged by the end of the season — double the 2023 figure and a 42 per cent rise on 2024.

Heat Ready London sets out five objectives and 37 priority areas spanning the short, medium and long term, across six sectors including the built environment, health and care, green space and infrastructure. Among the headline measures are expanding access to cooling spaces and public drinking water, retrofitting the highest-risk homes, increasing tree cover and urban greening, widening safe access to swimming and other ‘blue space’ recreation, and hardening transport infrastructure against extreme heat.

Transport for London says more than 190 Tube trains — about 40 per cent of the Underground — are now air-conditioned, alongside every London Overground and Elizabeth line train, with air-conditioned Piccadilly line and DLR trains to follow. All new double-decker buses carry air cooling, and water refill points have been added at stations.

Sir Sadiq framed the plan as a matter of social justice, noting that people in poorly designed homes, those without access to green space, older people, young children and those with physical or mental health conditions are most exposed. The mayor said he was ‘proud to unveil Heat Ready London’, describing it as “a call to action to our partners to use this framework to drive collective delivery so we can protect lives and strengthen the resilience of our city”. He added: “We must act now.”

Deputy mayor for environment Mete Coban said the plan, developed in partnership with London Councils, set “a new benchmark for how cities across the UK can respond to heat risk”, stressing that “high temperatures do not affect everyone equally”.

Professor Emma Howard Boyd, chair of the National Heat Risk Commission and former chair of the London Climate Resilience Review, welcomed the mayor’s leadership but warned that “extreme heat already hits hardest in the most deprived communities”. Cooling the city through trees, parks and shaded streets, she said, “does more than bring temperatures down: it cleans our air, reduces flood risk and makes neighbourhoods better places to live”.

London Fire Commissioner Jonathan Smith said extreme heat was “becoming an increasingly regular risk”, pointing to investment in new wildfire equipment and training since 2022. Mayoral health adviser and London GP Dr Tom Coffey said heat was now “the greatest risk to health from climate change in the UK”, warning that “in London we are reaching a tipping point”.

Greens: ‘this plan doesn’t go far enough’

The plan drew a pointed response from Zack Polanski, the Green party London Assembly member and the party’s assembly lead on the environment, who has repeatedly questioned Khan over the capital’s adaptation to a warming climate.

Polanski welcomed the plan as ‘a step above the Government’s dangerously complacent “wing-it” approach to planning for extreme weather’ but said it fell short of the scale of the challenge. “The fossil-fuelled climate emergency is making London’s summers hotter and more extreme,” he said. “But the mayor’s plan doesn’t go far enough. This plan lacks the funding, timelines and urgency needed to meet the scale of the challenge. We cannot afford to wait years for long-term solutions while people suffer through increasingly dangerous heatwaves.”

He called for an emergency effort to help households, businesses, schools, care homes and hospitals stay safe with measures that could be introduced immediately. Most alarming, he argued, was the plan’s failure to back calls from workers and trade unions for a legal maximum working temperature. “In the absence of proper legislation, workers who cannot perform their jobs from home are being left to endure extreme working conditions where heat exhaustion can quickly kick in,” he said. “No one should be forced to work in dangerous conditions without clear legal limits and enforceable protections to keep them safe.”

The mayor has already moved to tackle overheating through the London Plan, which requires new homes to be designed to stay cooler using shading, ventilation and smarter design. City Hall points to 4,000 free water refill points, more than 100 water fountains and over 640,000 trees planted since 2016. But with much of London’s existing housing stock still vulnerable, ministers, councils and the housing sector will need to act in concert to keep Londoners safe as the mercury climbs.