Lancashire and North Yorkshire are braced for “very severe and heavy” rain since this morning.
More than 100 extreme weather warnings, including 15 noting conditions were life-threatening, have been issued across the Britain.
Up to 100mm of rain is expected to fall in a matter of hours on Saturday in Lancashire, which has been placed on Red alert – the Met Office’s most extreme warning – ahead of the downpour.
The Met Office warned: “widespread flooding will lead to high levels of disruption to travel, deep, fast-flowing watercourses and an associated possible danger to life.”
On average, 145mm of rain usually falls in the entire month of December – a total forecasters predict will be surpassed in just hours of torrential rain in Cumbria, Lancashire and Yorkshire.
In the north, the Scottish Environment Protection Agency issued eight flood warnings and five flood alerts.
The government body advises Lancashire residents to “be prepared, move valuables and take advice from emergency services about evacuation.”
The Environmental Agency (EA) warned the River Calder, River Ribble and the River Wyre were all expected to flood.
Several rivers have overflowed their banks, including the River Calder and the Rochdale Canal, leaving houses and a bowling club flooded
Every river in Lancashire exceeded record levels, the Environment Agency said.
Flooding has brought travel “chaos” to roads in north Wales, with people rescued from cars and vehicles left stranded. Heavy rain has forced many British residents to evacuate their homes recently.
People can access information from council websites and the Environment Agency Floodline.
The agency is also operating a phone line – 0345 988 1188 – which will be staffed rather than offering recorded information.
The Army has been deployed and is helping with the response in several areas.