A Met Office yellow weather warning for most of the South West has been issued for thunderstorms.
The warning is in place between 8pm on Sunday 4 September and 4am on Monday 5 September.
It covers all of Cornwall, Devon, Dorset and Wiltshire, as well as most of Somerset.
The Met Office said: "Thunderstorms may cause some localised disruption on Sunday night.
"There is a good chance driving conditions will be affected by spray, standing water, locally gusty winds and/or hail, leading to longer journey times by car and bus.
"Some flooding of a few homes and businesses is possible, leading to some damage to buildings or structures."
The warning also says that lightning strikes could damage buildings and train delays and short-term loss of power is possible.
The Met Office said: "Heavy showers and thunderstorms are expected to develop across south west England on Sunday evening and move north across parts of Wales and Northern Ireland, clearing during the early hours of Monday morning.
"Whilst some places may not see much rainfall, a few places may see 20-30 mm fall in under an hour. Frequent lightning, hail and locally gusty winds are additional hazards that may accompany stronger thunderstorms, particularly across southwestern parts of England and Wales."