Dozens have been left homeless after houses were submerged in south Wales while a bolt of lightning set fire to flats in north-west London.
The downpours, in which parts of Devon received almost double their monthly average rainfall in just 12 hours on Saturday night, moved northwards across England during Sunday bringing atrocious driving conditions to the Midlands.
The gloomy weather saw typical temperatures in south-east England of 53F (12C) – some 18 degrees lower than during the blue skies and hot weather of the same time last week when the thermometer hit 86F (30C).
The Environment Agency issued a flood warning for the Old Basford area of Nottingham and 10 other flood watches for Oxfordshire and the Midlands while the Met Office issued six severe weather warnings for heavy rain throughout England on Sunday afternoon.
A Met Office forecaster said England and Wales would continue to have wet weather for most of the week, with Scotland and Northern Ireland escaping the worst of the summer showers.
A family were lifted to safety after fierce storm conditions trapped them on a beach surrounded by steep cliffs.
The three adults, one child and a dog were on a camping expedition at Labrador Bay near Brixham, Devon, on Saturday evening but rough seas prevented them getting back and they were eventually winched up the cliff by a rescue team.
Fire crews spent more than three hours pumping more than three feet of water out Lady's Mile Caravan Park in nearby Dawlish, while 40 firemen battled a blaze at a campsite near Corfe Castle, Dorset where lightening struck an electricity pole and started a fire in several caravans, trees and other buildings.
In Exeter, 93mm of rain fell in 12 hours overnight on Saturday – almost double the average monthly rainfall.
South Wales was one of the worst affected areas, with 100 homes were evacuated after flooding in Rhondda Cynon Taf.
Fifteen residents were looked after in a community centre at Rhydfelin, near Pontypridd, after three culverts were overwhelmed following torrential rain.
Mother-of-two Cerwen Price, 32, said: "It is ridiculous. Last weekend we were having a barbecue – now we are flooded out.
Councillor Maureen Webber, who represents the Rhydfelin Central ward on Rhondda Cynon Taf council, said there had been a series of floods on the estate over 30 years but the "force of the water was quite unbelievable".
She said: "I'm really upset to think people have had to suffer again because of the force of nature. It's ironic thing because we've just attracted a huge sum of money, somewhere in the region of £2.4m to alleviate the problem."
South Wales Police said they received around 450 calls about flooding in the Pontypridd, Cardiff and Caerphilly areas between 3pm and 11pm on Saturday.
Great-grandmother Gwyneth Austin, 81, suffered flooding to her Ystrad Mynach home. "The rain was so heavy – the street filled like a big pool," she said. "It was very sudden. I was shopping in Tesco and by the time I got back it was full up."
In some houses the flooding reached the ceiling and one person was admitted to hospital with a broken leg.
Eight fell runners were airlifted to hospital and another 25 were helped to safety after severe weather forced the abandonment of a race in Snowdonia.
In London, dozens were after a lightning strike started a fire at a block of flats in Barnes Wallis Court in Wembley.
Dave Elliott, a Met Office forecaster, said: "Thunderstorms are just as typical for June as the hot and sunny weather we've been having recently. England and Wales will remain unsettled for the rest of the week as far as we can see, with Scotland and Northern Ireland the best places to be because it will be drier overall."
