The Met Office has issued a yellow weather warning for thunderstorms for parts of England.
It said a band of heavy rain and thunderstorms was moving north from Devon and Dorset across to Somerset, Bristol, Gloucestershire and Wiltshire.
Some places could receive 30-40mm (1-1.5 inches) of rain between 08:00 and 12:00 BST on Sunday, along with a "risk of frequent lightning and hail". There could also be a risk of flooding in some areas, the Met Office added.
It advised people in flood risk areas to be prepared.