Two sinkholes forced the closure of parts of the M25 in both directions overnight, with chaos expected during the morning rush hour after London and parts of south-eastern England were drenched overnight.
Kent Police said an accident between junctions four and five, near Sevenoaks, had led to the discovery of two sinkholes on the central reservation. Highways England said it was assessing the “serious road defect” and the M25 would remain closed on Tuesday morning.
Highways England advised motorists to follow diversions.
Amber weather alerts were issued on Monday warning of flooding, transport disruption and a potential risk to life and property across the south-east overnight amid forecasts predicting a month of rain would fall in days.
The weather system has since moved north, bringing further downpours, flood warnings and warnings of “treacherous weather”.
Between 50mm and 60mm was expected over four to six hours in London and south-eastern counties until about 11pm on Monday. The average rainfall for the whole of June in the south-east is about 50mm, the Met Office said.
On Wednesday and Thursday, those regions plus northern Wales could be struck by 60mm to 80mm of rain, and possibly even up to 100mm.
Met Office meteorologist Alex Burkill described the figures as the “worst-case scenarios” but added that people need “to be aware that we’re in for some treacherous weather”.
“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 said.
June is usually the third driest month of the year, and the current weather stands in contrast to June 2018 where many stations saw less than 2mm.
The Environment Agency has issued a flood warning covering the River Wandle at Morden in south London, urging people to take immediate action as the flooding of properties was expected.
The agency said on its website shortly before 6pm on Monday: “River levels have risen as a result of localised thunderstorms. Flooding of property is expected imminently.
“Please take action. Further thunderstorms are forecast over the next six hours.
“We expect river levels to remain high until around 10pm on Monday evening.”
Residents are being told to plan driving routes to avoid low-lying roads near rivers which may be flooded.
A further six flood alerts warned people to prepare for potential flooding in parts of south London, Nottinghamshire, Wiltshire and Devon.
The Environment Agency’s executive director of flood risk management, John Curtin, warned there could be “issues all week” because the heaviest downpours were still to come. The overall flood risk has been set at “medium”.