A British record high temperature, 38.7 Celsius (101.6 Fahrenheit), may have been reached on Thursday, provisional data from the UK Met Office showed on Friday.
Soaring temperatures broke records in Germany, France and the Netherlands on Thursday, as a heatwave gripped Europe for the second time in a month.
The Met Office had said on Thursday that the second highest temperature ever in Britain had been recorded in Cambridge, England, at 38.1 C (100.58 F).
However on Friday, the agency announced a new provisional figure of 38.7 C, recorded at the Cambridge University Botanic Garden.
That would beat the country's previous record high of 38.5 C (101.3 F), recorded in August 2003.
"The temperature recorded yesterday at Cambridge University Botanic Garden will require quality control and analysis over the next few days and if validated, would become the highest temperature officially recorded in the UK," the Met Office said in a statement.
Heatwaves are extreme weather events, but research shows that as the planet warms they are likely to become more frequent.
Met Office projections show that heatwaves with the intensity of last summer could occur on average as regularly as every other year by the middle of the century.