Intense thunderstorms may bring the heatwave in Britain to an end, but there is still a chance of record-breaking temperatures.
Thursday saw the highest temperature recorded in the UK since 2015 with Wisley in Surrey hitting 35.1C (95.2F)- and the mercury could soar to a stifling 37C (98.6F) on Friday.
But the long hot summer is being disrupted with thunderstorms, which have prompted the Met Office to issue a weather warning.
Froecasters said thunderstorms have already broken out in eastern areas, with intense storms forecast for Friday afternoon and evening across eastern parts of England and north-east Scotland into Saturday before fresher conditions make their way east across the UK for the weekend.
Will Lang, chief meteorologist at the Met Office, said: “The heatwave conditions are coming to an end but it’s another hot day in the east and south-east of England today with temperature expected to reach 36C (96.8F) or 37C (98.6F) in places.
“If conditions all come together there’s a 50% chance that we will break the July record temperature and a 20% chance of a new all-time UK record high.”
A temperature of 36.7C (98F) at Heathrow on July 1 2015 is currently the record for the month of July, while the all-time record in the UK is 38.5C (101.3F) at Faversham on August 10 2003.
Mr Lang added: “Whilst many places will remain dry, the thunderstorms could lead to torrential downpours in places with as much as 30mm (1.2in) of rainfall in an hour and 60mm (2.4in) in three hours.
“Large hail and strong, gusty winds are also likely and combined could lead to difficult driving conditions as a result of spray and sudden flooding.
“There will also be some showers up the western side of the UK this evening and this heralds a more changeable and windy weekend.”
Sunday will be a wet and windy day, with weather warnings issued for rain and gales.
Southerly winds will gust at around 35mph-40mph and up to 50mph for exposed coasts and hills, while rain will be most persistent over hills with parts of the Brecon Beacons and Dartmoor potentially seeing as much as 60mm-80mm (2.4in-3.2in) of rain, the Met Office said.
Tony Wafer, RNLI community safety manager, said: “If you are heading to the coast this weekend, please find out where your nearest lifeguarded beach is and ask the lifeguards for advice on conditions, especially if you are going in the water.
“RNLI lifeboats and lifeguards have had four times as many rescues of inflatables so far this summer than they did last year.
“They can be very dangerous and we urge the public to respect the water when having fun using inflatables this summer.
“Please do not use inflatable toys or kayaks in offshore winds or big waves. If you are at a lifeguarded beach, an orange windsock indicates offshore winds.”
Meanwhile, police forces have been called following concerns for people’s welfare at rivers and a lake.
Thames Valley Police said a man’s body was recovered from the Jubilee River in Slough, adding that his death is not being treated as suspicious.
Warwickshire Police said emergency service personnel searching for a 17-year-old boy who disappeared after getting into difficulty in a quarry lake in Bishops Itchington, near Leamington Spa, have recovered a body.
Essex Police said the search for a boy who was last seen in water near Clacton Pier on Thursday evening resumed on Friday morning.
The force was called amid concerns for the welfare of two teenagers and were on the scene just after 6.35pm.
One boy was rescued by a lifeboat crew, checked over by medical teams and reunited with his family, but the second, aged 13, remains unaccounted for.
Elsewhere, cross-Channel rail operator Eurotunnel has cancelled thousands of tickets after “extreme temperatures” caused major disruption to services.
It is one of the busiest weeks of the year for cross-Channel travel as the start of many school summer holidays leads to a surge in family trips.
The company took the “unprecedented decision” to stop passengers travelling on Friday if they were due to return on the same day or Saturday in a bid to ease long queues.
On the trains, passengers were urged to avoid travelling on London North Eastern Railway (LNER) on Friday after lightning damaged the signalling system.
LNER operates trains on the East Coast Main Line between London and Scotland.
Train firm Northern advised passengers not to travel in the Yorkshire area due to the same issue.
On the roads, motorists were warned ahead of lightning, flash flooding and large hailstones, with a thunderstorm warning in place for Friday afternoon until just before midnight.
Temperatures were forecast to be in the mid-30s for much of east and south-east England, reaching 37C (98.6F) in London, and could rise higher still if there is a lot of sunshine.
A mix of toxic air, extreme highs, emissions from the continent and a lack of cloud cover caused a “high” air pollution alert to be issued for London.
Elsewhere, authorities said the heatwave was causing “winter conditions” in parts of the NHS, while many nurses were said to be dizzy and exhausted.