A yellow weather warning has been issued over South Wales for Saturday, 10 June for a thunderstorm that is predicted to occur between 2pm and 9pm on Saturday.
The Met Office has said that while many places will remain largely dry, thunderstorms with rain and hail are likely to take place in some areas over the afternoon.
High temperatures developing across parts of England and Wales on Saturday are expected to trigger a scattering of showers across this area, some of which are likely to be torrential and thundery, bringing 30-40mm in an hour.
Some places may see more than 60mm of rainfall, and strikes of lightning and strong winds are possible.
Spray and sudden flooding could occur, making driving conditions difficult. Power cuts may also occur and there is a small chance of businesses and homes being flooded.