Hundreds of thousands of Londoners lost more than four hours sleep a night during the June heatwave, according to a new survey.
The YouGov study for Greenpeace also showed an even larger number of people in the capital missed out on between three and four hours sleep.
The findings come as the capital is in the grip of its third heatwave of the year.
Temperatures are forecast to rise to 33C on Thursday and to be at least 30C until Saturday, according to the Met Office, with the risk of thunderstorms at the end of the week.
The UK Health Security Agency has upgraded its yellow health warning for the capital, the South East and other regions, to amber from Wednesday.
Thames Water has also urged Londoners and its other customers to stop using hosepipes to water their gardens or clean their cars as the South East bakes in unusually hot weather, with the signs growing of the threat from global warming.
YouGov interviewed more than 2,000 adults in the UK including 187 in London.
The small sample for the capital means the findings for the June heatwave need to be treated with caution but they show:
* Two thirds (66%) of Londoners said they struggled to sleep as the city was hit by tropical nights with temperatures not dropping below 20C
* Out of those who missed out on sleep, 45% said they lost between an hour and two hours
* 30% said they lost between three and four hours
* 14% said they lost more than four hours
* A majority (51%) of Londoners said their homes were uncomfortably or dangerously hot
* 30% said they had trouble travelling due to heat-related disruption
* One in five (20%) said they or someone in their household felt unwell
* 46% said their workplace was too hot
* 31% said they were less productive at work
Mel Evans, head of climate at Greenpeace UK, said: “This data exposes the brutal reality of dragging our feet on climate action in the UK.
“Heatwaves are no longer just a novel inconvenience, they are a creeping health, housing, and economic emergency that is costing families money they don’t have.
“The Government must stop big polluters from heating up our planet and make sure they pay at least some of the costs of cooling our homes, securing our national infrastructure and protecting public health.”
Forty-eight per cent of Londoners backed a levy on high-polluting companies, according to the survey.
* YouGov interviewed 2,135 adults across the UK between 30th June and 1st July 2026. Data were weighted.
