Temperatures in Britain reached a record high of 38.7 degrees Celsius on July 25, the Met Office national weather service said on Monday, confirming a preliminary reading.
"The reading at Cambridge Botanic Garden has been quality controlled and is officially the highest temperature on record in the UK," the Met office said in a tweet.
The previous record was 38.5C recorded in Faversham in Kent in southeast England in 2003.
"The UK joins Belgium, Germany and the Netherlands in breaking national temperature records," the Met Office said.
Mark McCarthy from the Met Office National Climate Information Centre said temperatures in Britain had been going up since the mid-20th century.
"Climate change has increased the likelihood and severity of heatwave episodes across Europe, which will have also increased the risks of a 40.0C temperature event in the UK," he said.