Britons should brace for a sleepless nights and scorching days as temperatures rise to potentially record-breaking levels over the next three days.
Heatwave thresholds are set to be smashed in central and eastern parts of England, with a "60 per cent chance" the UK could see its hottest-ever July day this week.
Forecasters expect the mercury to hit around 37C in London and the south east on Thursday, beating the current July record of 36.7C set at Heathrow airport in 2015.
Met Office meteorologists also said there is a “30 per cent chance” that Thursday's heat could surpass the UK's all-time temperature record of 38.5C, which was set in Faversham in August 2003.
Chief meteorologist Paul Gundersen said: "The UK will experience another pulse of high temperatures this week, with the possibility of records being broken for not only July but also all-time records.
“The weather setup is broadly similar to the pattern that brought high temperatures to much of continental Europe at the end of June.
“As well as high temperatures during the day, overnight temperatures will also be notably warm and could also break records. Conditions will feel much more comfortable for all by the time we get to Friday."
Widespread sunshine is expected across the UK on Tuesday, with temperatures in the low 30s in England, the east of Wales and as far north as Yorkshire.
But later in the afternoon thunderstorms will move into western England, bringing heavy thundery showers from the early evening spreading northwards into Wales before dissipating in the early hours of Wednesday.
Meanwhile, London and parts of the south east won’t see any respite from the blistering sun, with highs of around 34C tomorrow, according to the Met Office.
But Thursday is expected to see the peak in temperatures with 37°C possible in London, which would make it the hottest day of the year so far.
Thursday’s scorcher could also bring the hottest July night on record as sweltering days continue to give way to sticky evenings.
Temperatures could hit a record-breaking 24C overnight into Friday, Met Office forecaster Helen Roberts told the Standard.
The UK's hottest ever night so far was recorded in August 1990, when the mercury reached a staggering 23.9C.
People in affected areas are being urged to stay out of the sun, drink plenty of water and check on older neighbours and asthma sufferers.
Asthma UK clinical lead Dr Andy Whittamore said: "A toxic cocktail of hot humid weather and rising pollen levels this week could be extremely hazardous for the 5.4 million people in the UK with asthma, triggering deadly asthma attacks.”
Public Health England scientist Owen Landeg said the summer heat brings "real health risks" for older people, young children and those with underlying health conditions.
"If you're able, ask if your friends, family or neighbours need any support," he said.
Animal welfare charity Dogs Trust has also urged owners not to leave their pets alone in hot cars as it can prove fatal.
On a day with temperatures at 22C, the temperature inside a car could rise by 11C in just 10 minutes and quickly become dangerous, it warned.
