Temperatures are expected to reach highs of 25C to 26C, which is about 8C above average
Heavy showers will hit parts of the UK which could lead to thunderstorms and flooding, the Met Office said.
Showers are forecast to drift in from the south overnight into Sunday, which could turn heavy and potentially thundery during the day, Met Office meteorologist Jonathan Vautrey said.
The heavy showers will mainly affect the West Country, South Wales and parts of the West Midlands.
Meanwhile, temperatures are expected to reach highs of 25C to 26C, which is about 8C above average for the time of year, Mr Vautrey said.
There could be “heavy, short sharp” bursts of rain and hail and lightning, he said, adding: “As is the case with thunderstorms, they’re often quite hit and miss.
“Obviously it has been a pretty dry spring so for many areas rain is needed, but because of the heavy nature of these showers, splashing on to hard surfaces, there is the potential for minor localised issues and flooding.”
Between 20mm and 30mm of rain could fall within a couple of hours, or as much as 40mm in three hours, the forecaster said.
Motorists have been urged to take care when driving and be aware the thunderstorms “could come on at very short notice”, Mr Vautrey added.
Showers are also expected in Northern Ireland and Scotland on Sunday and Monday.
The wet weather could also continue on Monday in southern and western areas of the UK, and the Met Office is monitoring for any further warnings.
From Tuesday, the high pressure will rebuild and dry conditions and sunshine will return across the country, with temperatures in the low to mid 20s.
