The Met Office has issued a thunderstorm alert for England and Wales, warning there is a chance homes and businesses could flood quickly.
The yellow weather warning will cover large areas of southern England and south Wales tonight (15 May).
The Met Office explained that although the exact locations which could be affected remain uncertain, a few places may experience a combination of heavy rain, frequent lightning and hail.
A spokesperson for the weather service said: "Should thunderstorms develop, they are likely to move north from the south coast during Sunday evening into parts of south Wales, southern England and East Anglia overnight before gradually weakening during Monday morning.
"Whilst some places will remain dry, a few places may see 20-30 mm of rain fall in less than an hour, with frequent lightning and hail additional hazards."
The weather warning will be in place between 8pm today and 5am tomorrow.
Met Office explains what to expect
There is a small chance that homes and businesses could be flooded quickly, with damage to some buildings from floodwater, lightning strikes or hail
Where flooding or lightning strikes occur, there is a chance of delays and some cancellations to train and bus services
Spray and sudden flooding could lead to difficult driving conditions and some road closures
There is a slight chance that power cuts could occur and other services to some homes and businesses could be lost
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