A weather warning has been issued for Lancashire and the North West from Sunday night.
The Met Office says thunderstorms may develop late Sunday bringing torrential rain and lightning, with possible flooding and disruption to travel.
There is a small chance that homes and businesses could be flooded quickly, with damage to some buildings from floodwater or lightning strikes
The Met Office warning runs from 7pm tomorrow night.
The overall risk of thunderstorms on Sunday is said to have reduced.
But they may develop later in the evening.
A spokesman said: "Spells of rain are expected to affect many areas, perhaps turning heavy and thundery in some areas during the evening.
"Where thunderstorms develop, 20 to 30 mm rain may fall in a few places in an hour."