People are warned to drink plenty of fluids and keep out of the sun before severe storms forecast for this evening
Britain is expected to experience another scorching day as temperatures top records set on Thursday.
The hot and humid conditions across the country follow overnight storms that saw heavy rain, thunder and lightning.
And those downpours will return again on Friday night to disappoint Britons hoping for a sun-packed weekend.
Forecasters predict they are likelier to be even heavier than those experienced late on Thursday night and in the early hours of Friday.
"Today, we are going to see the highest temperatures of the year so far and we are expecting them to hit 32C," said Sky weather producer Rebecca Yussuf.
"However, we expect overnight tonight will be a repeat of last night, only more so, particularly over England, Wales and Scotland as heavy storms come up from France.
Temperatures in London will pass the 29.2C they hit on Thursday
"There is a real risk of torrential downpours of heavy rain, hailstones, frequent thunder and lightning.
"I wouldn't be surprised if some people see some flooding within the next 24 hours."
The Met Office has upgraded its warning from yellow to amber, saying: "Where thunderstorms do form, some torrential downpours are likely with frequent lightning, large hail and locally strong gusts.
"Significant flooding is possible where these do occur from surface water as well as from small, fast-responding watercourses."
John Curtin, director of incident management at the Environment Agency, said: "Intense heavy rainfall this weekend brings a surface water flood risk for England throughout the weekend.
"Flooding can happen very quickly and the public are urged to keep checking local weather forecasts and the Environment Agency website for information on a regular basis.
"We will continue to monitor the situation closely and support local authorities, who will respond to any reports of surface water flooding. We will also continue to monitor river levels closely and issue warnings where flooding is likely."
Thursday was until now the hottest day of the year, with temperatures touching 29.2C.
The hot, humid conditions have brought health warnings from Public Health England (PHE).
It urged people to drink plenty of fluids, keep out of the sun while it is at its hottest, and to wear at least factor 15 sun cream for skin protection.
It has also called for people to look out for children and the elderly, who are most at risk.
A former journalist and two Newcastle United fans are among the British victims who perished in the horrific mid-air disaster
Briton Glenn Thomas was one of nine UK nationals on board flight MH17 when it crashed in eastern Ukraine, colleagues said.
Two Newcastle United fans, John Alder and Liam Sweeney, who were travelling to see their football team play in New Zealand, also died in the crash, according to NUFC.com and the Newcastle Evening Chronicle.
Newcastle United fan Liam Sweeney
Mr Thomas, 49, was among 100 delegates reportedly on their way to an international conference on Aids in Melbourne, Australia.
He was a media officer at the World Health Organisation (WHO) in Geneva where friends today spoke of their shock and loss.
Fadela Chaib, a spokeswoman for WHO, said: "We have lost a wonderful person and a great professional. Our hearts are broken. We are all in shock."
Dr Lange is believed to have been with partner Jacqueline van Tongeren
Some of the great minds in the fight against HIV and Aids were on their way to the International Aids Society (IAS) summit, including, it is understood, one of its former presidents Dr Joep Lange, a well-known researcher from the Netherlands.
"If this is the case then the HIV/Aids movement has truly lost a giant," the IAS said in a statement.
Among the 283 passengers and 15 Malaysia Airlines cabin crew on board were also 173 Dutch nationals, 44 Malaysians, 27 Australians, 12 Indonesians, four Germans, four Belgians, three Filipinos, one Canadian and a New Zealander.
Albert Rizk and his wife Maree were returning from a holiday in Europe
In a bizarre twist of fate, 41-year-old flight attendant Sajid Singh swapped flights to fly on MH17 - months after his wife swapped off the doomed MH370 which vanished flying from Kuala Lumpur to Beijing, his his father Jijar Singh told The Malaysian Insider.
Kaylene Mann, from Queensland, Australia, who lost her brother and sister-in-law in the flight which disappeared on March 8, 2014, is now mourning the loss of her stepdaughter Maree Rizk, who together with her husband Albert, were were aboardMH17 on their way back to their Melbourne home after a month-long European holiday.
Sailor and businessman Nick Norris, 68, was also on his way home from a breakaway in Europe with his three grandchildren, Milo Maslin, 12, Evie Maslin, 10, and Otis Maslin eight, aboard the airliner, Perth Now reported.
Cor Pan posted a picture of the airliner on Facebook before he boarded it
The children's parents were said to be devastated, while Mr Norris's daughter Natalia Gemmell, said her father was a "great man" and described her niece and nephews as "gentle, clever and beautiful kids".
The Australian media also reported a much-loved nun, Philomene Tiernan, from Sydney, Toorak college teacher Frankie Davison and her husband Liam, studentElaine Teoh and her Dutch boyfriend Emiel Mahler and security consultant Marco Grippeling, from Melbourne, among the victims.
Young Dutchman Cor Pan, from Volendam, north of Amsterdam, who is also believed to have perished in the disaster, posted a picture of the jetliner on Facebook, minutes before he boarded it, writing: "If it should disappear, this is what it looks like."
Nine Britons are among the 298 victims on board a passenger plane reportedly brought down by a surface-to-air missile.
Moscow has hit back after the Kiev government claimed pro-Russian separatists shot down a passenger plane, killing all 298 people on board, including 173 Dutch and nine Britons.
Malaysia Airlines flight MH17 was heading from Amsterdam to Kuala Lumpur at an altitude of 33,000ft (10,000m) when contact was lost on Thursday afternoon in eastern Ukraine, close to the border with Russia.
It came down near the village of Grabovo, Donetsk in an area where Ukrainian forces have been fighting the rebels.
An emergency worker at the scene of the crash
An adviser to Kiev's interior ministry said the Boeing 777 was hit by a Buk ground-to-air missile and its president Petro Poroshenko called it an "act of terrorism".
But the Russian defence ministry reportedly pointed the finger at its neighbour, saying it picked up radar activity from a Ukrainian Buk missile system south of Donetsk when the airliner came down.
Glenn Thomas was among the victims of the tragedy
Sky's Katie Stallard said: "That doesn't correlate with the geography. This was a plane flying over territory that the Ukrainian government would perceive as friendly. Territory that they control.
"It is a slightly counterintuitive suggestion that they would perceive that aircraft as a threat when it is heading away from their friendly airspace and towards the Russian border."
Flames rise from wreckage of the Malaysia Airlines jet
Separatist leader Alexander Borodai said Ukrainian government forces were responsible, and Russian President Vladimir Putin said: "The state over whose territory this occurred bears responsibility."
However, a US official said Washington strongly suspected it was brought down by a surface-to-air missile fired by rebels.
Malaysia airlines flight MH17: Videos online show downing of plane.
At least 28 Australians were among 298 people on board a Malaysia Airlines passenger jet which was shot down over Ukraine with the loss of all on board.
Flight MH17 was en route from Amsterdam to Kuala Lumpur when it was apparently blown out of the sky by a missile over rebel-held territory near Ukraine's border with Russia.
Several videos have emerged online reportedly showing the crash.
Australians among dead after Malaysia Airlines jet shot down by missile over Ukraine.
Twenty-seven Australians died when a Malaysia Airlines passenger jet crashed in Ukraine, killing nearly 300 people on board.
Flight MH17 was en route from Amsterdam to Kuala Lumpur with when it disappeared from radar screens near Ukraine's border with Russia, prompting speculation it was shot down by a missile in the restive region
