Here are some of the key temperatures that could be matched or surpassed before the weekend:
33.3C: highest temperature recorded so far this year, on July 23 at Santon Downham in Suffolk
34.5C: highest recorded last year, on June 21 at Heathrow airport
35.6C: highest recorded in 1976, on June 28 in Southampton
36.7C: highest July temperature on record, set on July 1 2015 at Heathrow airport
38.5C: highest temperature ever recorded in the UK, set on August 10 2003 at Faversham in Kent
