Downpours are drenching parts of the UK but the heaviest rain is still to come, forecasters have warned.
The rain swept in overnight, with the heaviest in the South East where 0.6in (15mm) fell in 12 hours in Sellindge in Kent, the Met Office said.
But forecaster Steven Keates warned that heavier and more persistent rain is likely to hit southern and eastern England on Monday afternoon.
The Met Office has issued four yellow severe weather warnings for rain up until Thursday, saying that affected areas could see local flooding and disruption to transport.
The first is in place from 4am on Monday until the end of the day and covers an area from the Humber all the way down to the south coast, and from the East Midlands to Portsmouth.
Keates said the northern Home Counties, East Midlands, Lincolnshire and Humber could see some of the heaviest and most persistent rain.
He added: “The rain started to push in overnight as expected but nothing particularly heavy so far.
“The heaviest and most persistent rain is still to come.
“Probably later this afternoon into this evening and tonight we could see some of the heaviest rain.
“It is going to be more the persistence of the rain in some places and the intensity for others.
“Eastern and southern England in particular are likely to be seeing long and persistent bad weather.
“Some places could see a month’s worth of rain in two or three days, and we could see some flooding issues.”
The Environment Agency (EA) has one flood alert on the River Ravensbourne in London covering the boroughs of Lewisham, Bromley, Greenwich and Croydon.
It said there was a risk of flooding for low-lying land, gardens and roads that are close to the river between 7am and 6pm.
The EA added: “We are actively monitoring the situation and are prepared to respond if required.
“Please avoid using low-lying footpaths near local watercourses and plan driving routes to avoid low-lying roads near rivers, which may be flooded.”
The band of rain will move slightly north and west before settling, with Northern Ireland and Scotland expected to see the best of the weather.
Weather warnings are in place for the whole of Tuesday and up until midday on both Wednesday and Thursday for north-eastern England down to the Wash and as far west as the West Midlands.