A weather warning saying heavy rain could lead to flooding has been issued for large parts of south-east England into this morning.
The Met Office's yellow alert, running until 10am on Monday, covers an area stretching from Chichester in West Sussex to Canterbury in Kent.
Homes and businesses could be hit by a deluge and public transport could be affected, the forecaster said.
The Environment Agency has four flood warnings and 39 flood alerts in place, mainly across south-eastern parts of England.
Met Office forecaster Simon Partridge said: "We are expecting to see 15 to 25mm of rain but it's basically mainly associated with some heavy showers.
"So a lot of it is to cover the potential for some very tricky driving conditions tomorrow morning, being obviously Monday morning so one of the busiest."
Mr Partridge said the rain in the South East will ease off later on Monday but showers are predicted across the UK for much of the coming week.
The fresh front of rain overnight comes after a yellow alert was put out by the Met Office to cover the South East earlier on Sunday.
Plumpton, near Lewes, East Sussex, received 39mm of rain in 24 hours - more than a third of the average monthly rainfall for the area, the forecaster said.
Parts of the North West will also see heavy rain on Sunday night, it said. Showers will move northeast across northern areas on Monday and be heaviest over hills.
On Tuesday, areas across the UK will see downpours, which will ease on Wednesday, the weather agency added.
Rain will hit the North West again on Thursday, although there will be drier conditions further southeast.
This comes as on Sunday images of rubbish bins floating down the streets emerged - and cars were seen left partially submerged.
Adam Hartley, 50, a creative director at a PR agency, said he awoke to find flooding outside his door in Haringey, and has called for more to be done to resolve London's "unfit-for-purpose sewage and drainage systems".
He said: "The problem is that I live at the bottom of two steep hills in Muswell Hill.
"So every time it rains the leaves and dirt flush down the hill and block the drains on our road.
"I'm lucky, in that I'm (reasonably) young, healthy and capable enough to put on some wellies and wade through the remnants of the flood."
UK 5 day weather forecast
Windy with showers, also longer spells of rain in the west.
Today:
A windy and rather cloudy day for many areas with scattered showers and also some longer spells of rain in the west. Driest and brightest weather in the east.
Tonight:
Band of heavy rain and very squally winds affecting western areas during the evening, easing as it moves east overnight. Clear spells and blustery showers following into the west.
Tuesday:
Rain in the east turning more showery as it clears, then windy with a mix of sunshine and showers, heaviest and most frequent in the west with possible thunder.
Outlook for Wednesday to Friday:
Heavy showers in places on Wednesday, with sunny or clear spells between, easing later. Rain for northwestern areas Thursday and Friday, drier further south and east; becoming very mild and windy.
