The last time temperatures were as high was on March 30, with 24.5C recorded in London.
Other parts of the South East, Wales and the North West are predicted to see top temperatures of around 20C.
Oli Claydon, from the Met Office, said: “Showers will start to ease and temperatures will increase over the bank holiday.
“There’ll be highs of up to 23C for central parts of England and possibly into London.
“There is a slow progression towards warmer and drier conditions.”
Wet weather has dominated the forecast this month, with Wales recording 200.7mm of rain – double the monthly average – making it the wettest May in records dating back to 1862.
Dorset, Bristol and eastern parts of Scotland have also been particularly hard-hit by downpours.
Across the UK, it has been the 10th wettest May on record, according to Met Office figures.
Despite some respite over the weekend it looks like the sunny spell could be short-lived, with forecasters warning showers and cooler weather could return early next week.