Half a month’s rain fell in a few hours overnight, causing travel chaos across the southeast of England.
The downpour caused railway stations in Didcot, Newbury and Chieveley in Berkshire to suffer severe flooding.
The Met Office has since issued amber warnings across the east, south and southeast.
Martin Combe, a meteorologist from the Met Office, said that 32.88mm of rain fell in just three hours in Farnborough, Hampshire.
"The showers and thunderstorms are going to carry on for quite some time, moving slowly north and eastwards, remaining around London through the morning and all afternoon in East Anglia," Mr Combe said.
Fire chiefs are advising motorists to avoid unnecessary journeys following reports of waterlogged roads across the country.
A Thames Valley Police spokesman said: "Roads are severely disrupted, including the M4 at the A34 junction with Newbury, the M40 throughout the Thames Valley and in particular the Watlington and Stokenchurch area."
The news comes as torrential rain caused a London Midland train to derail near Watford Junction.
Operators said the train was struck by a landslide caused by the downpour before being hit by another service passing by.
