Britain’s heatwave is to be followed by four days of “disruptive” thunderstorms this week, forecasters say.
The Met Office predicts the UK’s recent spell of sweltering hot weather will give way to heavy downpours and thunder and lightning, while some areas may be flooded.
By Monday lunchtime, thunderstorms had already hit parts of Devon, Cornwall and Wales, the Met Office said.
It said thunderstorms across north Wales, the North West of England and the West Midlands later on Monday afternoon could bring extreme rainfall.
Beach-goers camped overnight at the weekend to get spots on seaside resorts as councils warned the coastline was “extremely busy” and Britons were warned to stay away.
Temperatures reached 34C on Sunday, the fourth day in a row that thermometers in the South of England passed the 30C mark.
However, the Met Office has issued weather warnings covering almost the whole country from Monday morning, says there is “a small chance that homes and businesses could be flooded quickly” following rain showers, with the chance of “significant and disruptive” thunderstorms.
The far north of Scotland is the only part of the UK not currently covered by Monday’s weather warning, which is in place across the whole of England and Wales until at least Thursday.
Read more: Two dogs rescued after being left in hot car
It follows an intense period of very hot weather that saw temperatures reach 34C (93.2F) at Herstmonceux in East Sussex on Sunday.
Watch the video below
Met Office forecaster Craig Snell said: “For England and Wales over the next four days, there is a risk of some very severe weather in places but it is not going to be everywhere.
“Away from the thunderstorms, it is still going to be very hot.
“It is not going to be wall-to-wall sunshine, but it is not going to be a washout each day.”
The warning means there is a risk of torrential rain, hail, frequent lightning and strong gusty winds in much of England and Wales if intense thunderstorms break out.
Downpours could see 0.8in to 1.2in (20mm-30mm) of rain fall in an hour, with some locations potentially receiving 1.6in to 2.4in (40mm-60mm) in three hours.
The Met Office said these would be fairly isolated incidents, and the Environment Agency had only five flood alerts and no flood warnings in place as of 3:50pm on Monday.
Regarding Monday, Snell said: “The warning does not imply that everyone is going to see them (thunderstorms) – a lot of places will remain dry, sunny and hot – but we will see some fairly severe thunderstorms developing over the course of the day.”
The Met Office warned that flash flooding could cause travel disruption and power cuts, but also cautioned about the risks caused by fast flowing or deep floodwater.
It came as a 12-year-old girl died after going missing in the River Leven, near Ballock Bridge, Loch Lomond, in the west of Scotland on Sunday evening. Her body was discovered by emergency services hours later.
In Norfolk, a woman in her 30s died after getting into difficulties in the sea at Waxham on Sunday.
HM Coastguard dealt with 340 incidents across the whole of the UK on Saturday – the highest number of call-outs in a single day for well over four years.
Friday saw the hottest August day in 17 years, with temperatures hitting 36.4C at Heathrow and Kew Gardens in London.
Snell said: “We started this run of 30C days on Thursday, and Monday will be the fifth day where we will have those temperatures down in the south eastern quarter of the UK.”