An amber weather warning is coming into force and dangerous thunderstorms will hit the UK.
This weekend’s storms could cause flooding and pose a danger to life in some areas, the Met Office said.
Buildings could be damaged by floodwater, lightning strikes, hail or strong winds, the forecaster said.
Motorists have been urged to prepare.
Heavy rain with some thunder could create “fast flowing or deep floodwater, causing a danger to life” in the amber warning area, which spans the east and south east of England, including London, between 4am and 11am on Saturday.
Between 20mm and 40mm of rain could fall in one hour in the amber warning zone, going up to 70mm to 100mm in just a few hours where heavy downpours persist.
“Torrential rain, with thunderstorms in places, could lead to some significant surface water flooding during Saturday morning,” the Met Office said.
An ongoing deluge may cause “significant impacts” if it hits “more urban areas”.
It is likely that homes and businesses will flood and that flooding could happen quickly, the Met Office said, adding that some communities may be cut off if roads flood.
It is the first amber warning to be issued for London since January last year.
The warning expands to most of England and some parts of southern Scotland from midnight to 9pm on Saturday.
Forecasters said these storms could “cause disruption in places”.
“Areas of heavy rain with embedded thunderstorms will move north-westwards across a large swathe of central and eastern England through Friday night into Saturday,” the Met Office said.
It added: “Rain will likely be torrential in places, bringing 20-30mm in less than an hour, with 60-90 mm in two to three hours possible in a few places.”
Frequent lightning and localised surface water flooding are also possible.
⚠️⚠️ Amber weather warning issued ⚠️⚠️
— Met Office (@metoffice) July 18, 2025
Torrential, thundery rain across parts of southeast England
Saturday 0400 - 1100
Latest info 👉 https://t.co/QwDLMfRBfs
Stay #WeatherAware ⚠️ pic.twitter.com/BVzZAcVCco
Chief Met Office meteorologist Andy Page said: “Intense rainfall will impact parts of the UK as thunderstorms move in from France.
“A range of severe weather warnings have been issued, including an amber warning covering south-east England and London.
“The intense rainfall could lead to surface water flooding as well as frequent lightning and hail too.
“The situation is evolving, and warnings may be changed or added.”
He added: “This weekend is expected to be busy on the roads as more schools in England and Wales break up for the summer holidays, so it’s important people keep up to date with the very latest forecast.
“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.”
The persistent cloud and rain will keep the temperatures on Saturday relatively low.
Maximum temperatures will mainly stay in the high teens to low 20Cs, but brighter spells in the south could reach the mid to high 20s.
The most recent amber warning issued for London was for wind on January 2 2024, during Storm Henk which swept through central parts of England and Wales.
The AA has urged drivers to prepare for disruption and take care on the roads.
The breakdown service said: “This amount of rain is well over a month’s worth for a normal July.
“As well as heavy rain, impacts from frequent lightning, gusty winds and large hail are also likely.
“These storms could affect some of the popular holiday routes for early departures on this year’s summer getaway.
“While localised flash flooding and the sudden appearance of surface water are the usual dangers associated with summer heavy rain, the potential for slippery road surfaces at junctions and roundabouts is a hidden menace.”
