Met Office forecaster Marco Petagna said the mercury could reach 29C making it “potentially the warmest late August Bank Holiday on record which dates back to 1965.”
He said the UK’s previous top August Bank Holiday temperature was 27.1C heat which hit Santon Downham, east Anglia, on August 31 2009.
Predictions are for Monday’s temperatures to hit 28C or 29C in the south east and there is a 20% chance of it climbing to 30C, according to Mr Petagna.
He said the sun is very strong at this time of year so it does not take much for the heat to build up, particularly in urban areas.
It will be cooler in Scotland and Northern Ireland with 17C-20C predicted, while those in central and southern England along with South Wales may enjoy summer heat that is in the mid-20Cs.
The all-time highest temperature recorded in August was 38.5C in Faversham, Kent, on August 10 2003, the Met Office said.