Today is officially the hottest day of the year so far, with temperatures reaching 37.8C (100.04F) in Greater London.
The Met Office tweeted that Friday has been the “hottest day of the year by some way”.
Met Office spokeswoman Nicola Maxey confirmed the highest temperature was recorded in Heathrow, Greater London, on Friday afternoon.
She told Sky News: “Today is the hottest day of the year so far as 37.8C (100F) was reached at 2.41pm at Heathrow today.
“37.3C (99.1F) was reached at Kew Gardens at 2.55pm.
“Before today, only three days on record have seen temperatures that exceed 37C!”
Forecaster Simon Partridge added: “This not only makes it the warmest day of the year, it also makes it the third hottest UK day on record.”
The current temperature record was registered at 38.7C (101.7F) at Cambridge University Botanic Gardens last year, while the second hottest day was 10 August 2003, when the mercury rose to 38.5C (101.3F) in Faversham, Kent.
The first one was recorded at 37.1 (98.8F) in Cheltenham, Gloucestershire, on 3 August 1990.
The Met Office earlier warned that climate change was exerting an “increasing impact” on the UK, with data showing an “undeniable warming trend”.
However, the soaring temperatures are expected to be short-lived.
The Met Office has issued a thunderstorm warning for this afternoon, with a yellow warning in place from 4pm until midnight across large parts of east and southeast England where the weather will be at its hottest.
Gusty winds, hail and “frequent lightning strikes” can be expected, which could cause slight damage to buildings.
The Met Office said the storms will be caused by hot air moving in from mainland Europe, some parts of which will be cooler than the UK.
Popular tourist spots across Europe, including Ibiza, Lisbon and Berlin, are expected to reach 33C (91.4F), 30C (86F) and 25C (77F) respectively.
The Met said cooler air is arriving for the weekend as a cold front sweeps the UK in the next 24 hours.
Temperatures are expected to be closer to average tomorrow, but it will still be relatively warm in the South East.
Despite the short spike of hot weather, July has been below average temperature-wise.
“We’ve not seen a temperature anywhere above 30C (86F) so far or even with a three in it, that is quite unusual for July,” a Met spokesman said.