It has been the hottest late August bank holiday weekend ever – with temperatures reaching 32.7C (90.7F) 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.
The hot temperatures are expected to continue to rise this afternoon, forecasters say.
On Saturday a new record for Wales was set in Gogerddan, where 28.8C (83.8F) was recorded.
In Scotland, which does not have a late August bank holiday, temperatures were slightly cooler – but still reached 26C (78.8F) in Glasgow.
Last month, the UK’s highest ever temperature was officially recorded in Cambridge when 38.7C (101.7F) was measured.
It beat the previous UK record of 38.5C (101.3F), set in Kent in 2003.
UK weather: Hottest late August bank holiday weekend on record – BBC News