A weather warning has been issued for the north west with up to 60mm of rain expected to fall in exposed parts of the county, warn forecasters.
Localised flooding is possible as the large area of rain is expected to persistent until around 1pm today.
A Met office spokesman said: "A large area of rain will move into northwest England Monday night into Tuesday. This will be heavy and persistent in places with widely 20 mm falling and 40-60 mm possible in the most exposed spots.
"It looks most likely that parts of Lancashire and the surrounding areas will see some of the highest totals and so are more likely to see some disruption from localised flooding."