Heavy downpours across England are causing major disruption for road and rail users.
Network Rail said some areas had “suffered” two months worth of rainfall in one day with drains overwhelmed.
Rail operator Southern has advised people to avoid travelling, delay journeys or use alternative routes.
The M25 was closed in both directions for almost eight hours after two sinkholes were discovered following a crash at about 23:30 BST.
A total of 31 flood alerts are in place across the country, with some areas set to see up to 60mm of rain, particularly over the first half of the day.
Southern tweeted “train services running across the whole network will be cancelled or delayed”.
A Network Rail spokesman said engineers were “out in force” pumping water in the south east.
“Across the south east, we suffered over a month’s worth of rainfall in just one day and in some areas the downpours equated to two month’s rain,” he said.
“We’ll continue working to keep passengers moving and then we’ll review the drainage systems which have suffered problems to see if we can do anymore to avoid similar incidents in the future.”
Leicestershire Police said it was receiving a “high level” of calls about blocked roads, while a driver narrowly escaped injury after a tree fell on his car in Thurnby.
A woman in her 80s and her dog were rescued from a flooded property in West Kingsdown, near Sevenoaks in the early hours.
Kent Fire and Rescue Service said she had been trapped in her home up to waist height.
In Meeth, Devon, a thatched house caught fire when it was struck by lightning overnight. No-one was injured in the blaze.
Rain has also hit the Cricket World Cup for the second day in a row as Bangladesh’s game against Sri Lanka in Bristol has been delayed.
BBC Test Match Special’s Simon Mann said: “It’s a grim scene. Play today is extremely unlikely.”
Met Office meteorologist Alex Burkill said the UK was in for “some treacherous weather”.
Weather warnings are expected to remain in place for much of the day, with forecasters predicting parts of the UK could be inundated during the rest of the week.
North-eastern parts of England and the Midlands are expected to bear the brunt of the downpours on Tuesday, with a yellow warning in place until midnight.
The Environment Agency has issued three flood warnings in south-east England, for the River Wandle at Morden, south London, the Emm Brook at Wokingham and Ravensbourne at Bromley.
The agency said on its website: “River levels have risen as a result of localised thunderstorms. Flooding of property is expected imminently. Please take action.”
The Met Office said some parts of the country could see 60 to 80mm of rain on Wednesday and Thursday, possibly up to 100mm.
Mr Burkill described the figures as the “worst-case scenarios”.
“If you add it all up some places are likely to see over 100mm this week, which is around double the average they would get in the whole of June,” he added.
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