Heavy downpours across England are causing major disruption for road and rail users.
Rail operator Southern has advised people to avoid travelling, delay journeys or use alternative routes.
It tweeted “train services running across the whole network will be cancelled or delayed”.
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.
The M25 near Swanley is closed between junctions three and four, with a police incident causing “considerable congestion”.
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 the woman had been trapped in her home up to waist height.
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.
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.”
- Heavy rain and flooding cause disruption
- Flood risk warning for heavy rain
- Flash flooding after thunderstorm
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.
On Monday evening, heavy flooding in Kent closed all lines through Orpington railway station for several hours.