The Met Office has issued its first weather warning for a thunderstorm in its 164-year history, after days of sweltering temperatures.
The weather service introduced the new advisory for thunderstorms last month.
Sunday's warning said storms could develop in south Wales and south-west England throughout the day.
Forecasters warned it could lead to torrential rain, hail and lightning and there was a small chance of flooding for homes and businesses.
It also said the weather could lead to difficult driving conditions and road closures.
Source : BBC website