The UK is set to see its hottest day on record, with temperatures on Tuesday expected to reach up to 42C (107.6F).
A high of 38.1C was reached in Suffolk on Monday, just short of the UK record of 38.7C set in 2019. Wales recorded its hottest day on record with 37.1C.
The Met Office has issued a red extreme heat warning covering much of central, northern, and south-east England.
Provisional figures showed the UK experienced the warmest night on record from Monday into Tuesday.
Temperatures did not fall below 25C in places overnight, exceeding the previous highest daily minimum record of 23.9C recorded in Brighton on 3 August 1990, the Met Office said.
Thermometers were reading 39.1C in the village of Charlwood, Surrey, before 12:00 BST on Tuesday. If confirmed, it will be the highest temperature ever recorded in the UK.