Heavy rainfall caused localised flooding and led to major disruption overnight in the Lancaster and Galgate areas.
A number of roads were closed and residents evacuated from their homes.
Lancaster and Galgate were the worst affected with a number of properties flooded.
The A6 at Galgate was closed in both directions and 27 residents were housed in two nearby pubs.
Lancashire Police, Lancashire Fire and Rescue Service, The Environment Agency and Lancaster City Council responded jointly to over 500 calls related to flooding and attended over 100 incidents across the county.
Over 70 people and a number of animals were rescued.
Trains north of Preston were cancelled and diversions were in place in Devonshire Road, Blackpool, with a number of local and minor roads also affected.
Disruption to the road network is likely to continue throughout the day (Thursday November 23) and motorists are advised to allow extra time for journeys into Lancaster.
Drivers should avoid junction 33 or the M6 and use junction 34 instead.
A spokesman for Lancashire Constabulary said: “The flood gates around Garstang and Catterall were opened and coped well with the rain that fell.
“There was unprecedented flooding in Thornton Cleveleys, Cleveleys, Preesall, Galgate and on Devonshire Road in Blackpool.
“All agencies worked really hard in a co-ordinated effort to minimise disruption and protect the public and we will continue to support those communities worst affected.”
“The focus is now firmly on supporting those communities which have been most affected.”