Heavy rain with the risk of thunderstorms is expected to continue over the rest of the weekend, with warnings of potential flooding and travel disruption.
The Met Office issued a yellow warning for thunderstorms across large swathes of England and Wales stretching across the weekend and into most of Monday.
The warning says that spray and sudden flooding caused by the rain may lead to difficult driving conditions or road closures.
The south of England and Wales are likely to be the wettest areas over the whole weekend, with other parts of the country seeing dry and warmer weather.
The Met Office said 24.1mm of rain fell in an hour in Canterbury, Kent, on Saturday, which could lead to some surface flooding.
Becky Mitchell, a meteorologist for the Met Office, said the weekend was a ‘messy picture’.
She added: ‘The main thing over the next three days is the risk of thunderstorms in the south.
‘Saturday night is going to be pretty mild and then Sunday across the south it’s a picture of sunshine and showers – those showers could be thundery at times.
‘That risk is really within the warning zone – central and southern England and Wales could see some heavy downpours tomorrow.
‘Further north it’s going to be a bit drier with cloudy skies across the east coast.’
Bad weather including heavy rain and low cloud caused the cancellation of three commemorative flypasts by the Red Arrows.
The RAF display team had planned to fly over London, Cardiff, Edinburgh and Belfast to commemorate 75 years since VJ Day.
However, only the Belfast flypast took place as the other events were cancelled due to the bad weather.
In addition to the rain, forecasters expect the rest of the weekend to be much cooler after a week of hot and humid weather.
The Lake District town of Keswick in Cumbria saw the mercury rise to 24.8C on Saturday.
However, this was milder than much of the week, where temperatures above 34C (93.2F) were recorded for six days in a row.
The south of England and Wales are likely to be the wettest areas, with frequent lightning, gusty winds and heavy downpours with 30 to 40mm of rain possible in less than an hour, according to the Met Office.
Five flood alert warnings have been issued across the West Midlands by the Environment Agency.
Met Office chief meteorologist Frank Saunders said: ‘Up until Monday, thunderstorm warnings cover much of England and Wales, with parts of southern England and South Wales seeing the greatest likelihood of impacts.
‘The storms will not affect all areas, but where they happen there will be frequent lightning, gusty winds and intense, heavy downpours with 30 to 40 millimetres of rain possible in less than an hour and, in a few unlucky spots, a small chance of 60 mm falling in a short period.
‘With the continuing hot weather, large swathes of the UK continue to be at risk from thunderstorms, and potentially the impacts from heavy rain, into the early part of next week.’
Spokesman Oli Claydon, added: ‘The overnight temperatures remaining quite high will mean quite a close, muggy feeling that is in tune with thunderstorms being forecast all the way through to Monday.
‘Some areas could see up as much as 40-50mm (1½-2in) of rain in two to three hours [today], with 50-70mm (2-2½in) possible in three hours on Sunday.
‘There’s continued thunderstorm warnings through to Monday at the moment.’
Saturday’s outlook should be bright in the West but with thick cloud coming in from the North Sea in the North East, the Met Office said.
Mr Claydon added: ‘One thing to note with this kind of weather is it is important to keep an eye on the forecast as it can change quite quickly.
‘The nature of thunderstorms means it is quite tricky to be more specific as to exactly where. We can expect them anywhere in those yellow warning areas.’
Neil Davies, Flood Duty Manager at the Environment Agency, said: ‘Isolated thunderstorms could bring sudden surface water and river flooding, which may lead to flooded properties and severe travel disruption in some areas. Further surface water and river flooding is also a possibility until Sunday.’
The weather will be an added kick in the teeth for the thousands of Britons who made a mad dash across the Channel last night in a desperate bid to make it home before the government’s 14-day quarantine kicked in at 4am.
From 4am onwards, all those arriving from France must quarantine for 14 days after the country reported a spike in coronavirus cases.
The 11th-hour move sparked chaos for an estimated 500,000 British holidaymakers in France – including a couple who forked out £1,000 for business class Eurostar seats and a family who drove for 12 hours to get home.
One mother was forced to leave two of her children behind with her husband when she fled France on the last Eurostar train.
The woman – who had to return to the UK before quarantine began due to her job – was only able to get tickets for herself and her baby.
She now fears her two daughters – who will return on Monday – may not be out of quarantine when their school goes back.
The woman, who did not provide her name, told Sky News: ‘This has completely ruined our summer. I don’t know what I’m going to do now. I am so upset about this.’
There are also fears that the new rules will cause thousands of children to miss the start of the school year as pupils who do not return to the UK by Tuesday night will still be self-isolating at home when the majority of schools go back on September 2.
But with limited capacity on flights, ferries and the Eurotunnel, many will have no choice but to stay in France – or pay high prices for some of the remaining tickets.
Some tourists had less time to avoid quarantine after the Scottish and Welsh governments demanded the rules be introduced a day earlier.
Meanwhile, France is likely to impose to impose tit-for-tat quarantine restrictions from Monday for people arriving from Britain, meaning British travellers will have to self-isolate on arrival there too.