The unidentified woman was helped to safety after running into waters in Ellel earlier, the fire service said.
Fourteen flood warnings have been issued, including in Croston, which was hit by a severe deluge last year.
Some rail services between Preston and Lancaster have also been cancelled after heavy flooding on the track.
Read breaking news updates on BBC Lancashire Live
Elsewhere, Burrow Beck in Lancaster has burst its bank, and there are two flood warnings for the River Condor at Galgate amid prolonged periods of heavy rain.
No properties have been affected, although water is being pumped from culverts in some areas.
Dave Wilkinson, who lives in Galgate, said: "If the river levels keep up like this it's obviously going to come over in the next 24 hours I would say.
"This is just one night's rain. We've been here for six years now and it's never gone up as quickly as this before."
The Environment Agency's flood warnings mean flooding is "expected", with "immediate action required".
Police are advising people to avoid travelling where possible, to turn off electricity in their homes and avoid walking through floodwater.
Drivers have also been urged to exercise caution.
A pregnant woman was rescued from her car by a farmer after becoming trapped amid widespread flood warnings across Lancashire.