Thunderstorms and flooding could pose a danger to life in parts of the UK this weekend, according to forecasters.
The Met Office issued an amber thunderstorm warning for London and much of south-east England for 4am to 11am on Saturday, when heavy rain could cause “fast flowing or deep flood water”.
Yellow thunderstorm warnings are in place across much of England until 9pm, with 15 to 25mm (0.6 to 0.9 inches) of rain possible in under an hour. Scotland has a yellow warning for rain from 4pm on Saturday until midday on Sunday.
A prolonged downpour comes as thunderstorms move in from France that could “lead to some significant surface water flooding during Saturday morning” and may cause “significant impacts” in more urban areas, the warning said.
Frequent lightning and localised surface water are also possible, and motorists have been urged to take care. The weekend is expected to be busy on the roads as many schools in England and Wales break for the summer holidays.
The Met Office said flooding of homes and business was likely and could happen quickly, and that some communities may be cut off should roads flood.
“The situation is evolving, and warnings may be changed or added,” the Met Office’s chief meteorologist, Andy Page, said.
London is particularly susceptible to surface water issues during thunderstorms because of the prevalence of impermeable surfaces. Under the amber warning, 20 to 40mm of rain could fall in an hour, with as much as 70 to 100mm accumulating in just a few hours where heavy downpours persist.
“There will be spells of more pleasant weather in parts of the UK through the weekend, with some sunny spells in between systems as they move through,” said Page.
Temperatures are expected to stay in the high teens to low 20s with persistent cloud and rain, but could reach mid to high 20s in the south during brighter spells.
The amber warning is the first to be issued for London since January 2024, when Storm Henk swept through central parts of England and Wales, and comes after England experienced the hottest June since records began in 1884.
Scientists said earlier this week that record-breaking extreme weather was the new norm in the UK, with weather records showing that the climate had changed in recent decades as a result of carbon pollution emitted by burning fossil fuels.
