It has been the hottest late August bank holiday weekend ever - with temperatures reaching 33.3C (91.94F) in west London.
The Met Office confirmed the new record temperature, which was set at Heathrow.
It beats the previous record of 31.5C (88.7F), set in 2001 and again at Heathrow.
And BBC Weather said UK temperatures could reach similar levels on Monday - with highs of up to 33C in south-east England.
On Saturday a new record for Wales was set in Gogerddan, where 28.8C was recorded.
In Scotland, which does not have a late August bank holiday, temperatures were slightly cooler - but still reached 27C in Auchincruive, Ayrshire.