Heavy downpours across England are set to continue throughout the day, signalling the end of summertime.
The Met Office has issued a yellow warning for rain which could cause flooding in central and eastern areas of England until midnight on Tuesday.
Parts of Scotland, Wales and Northern Ireland will also experience wet weather throughout the day, but no warnings have been issued for these nations.
Much of the UK basked in sweltering sunshine at the start of the month, including Wales which experienced its warmest September night on record, while temperatures in Scotland reached the highest since 1906.
But grey skies and temperatures in the late teens hailed the end of summery weather towards the middle of the month.
Cars were captured ploughing through floodwater on Tower Bridge in central London beneath a blanket of clouds on Tuesday morning.
The capital is predicted to be one of the worst-hit areas in terms of rainfall in the morning, with up to 25mm of water predicted to lash London.
Met Office meteorologist Annie Shuttleworth said that as the rain moves north-eastwards throughout Tuesday, areas of the Midlands and north-east could see 40mm of rain.
She added that the rain is set to ease in the south on Tuesday afternoon, with a “low risk” of thunderstorms to follow.
Ms Shuttleworth said: “We have seen the main body of rain move further north throughout the morning, and the rain will persist for the longest in north-eastern parts of England.”
She added that Wednesday will bring drier weather across the UK, which is set to stay fairly settled with patchy sunshine predicted throughout the coming days.
Tuesday temperatures of around 18C (64.4F) in London and 15C (59F) in Edinburgh will climb to around 21C (69.8F) and 18C (64.4F) respectively on Wednesday, Thursday and Friday.
Meanwhile, temperatures in Cardiff and Belfast are predicted to remain constant at around 18C (64.4F) throughout the working week.
Ms Shuttleworth said that the long-range forecast for September is uncertain, but forecasters expect temperatures across the UK to be slightly higher than average for the time of year.
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