Brace yourself: the Christmas roads rush is coming. As many as 12 million cars will be taking to the roads over the December 24-26 period, the RAC has predicted.

Before then, the big getaway is expected to start in earnest on Monday, with drivers taking advantage of some of the lowest petrol prices for four years.

With unsettled weather likely, the RAC is urging drivers to prepare well for journeys.

The AA and the Environment Agency reminded motorists to stay out of flood water as they head off, after revealing that last Christmas Eve was the busiest day in the last five years for flood rescues.

The RAC said around four million cars will be on the road on Christmas Eve and about 4.6 million on Christmas Day.

RAC national operations manager Matt Dallaway said: "December has seen the UK's weather take on a distinctly unsettled and for some of us wintry flavour, and the signs are that this could continue through the week when many of us will be taking to the roads.

"So the message is for drivers to plan for their journeys ahead of time, and make sure their vehicles are properly winter-proof."

The AA said it rescued 642 vehicles from flood water on Christmas Eve last year, while the Environment Agency issued 450 flood warnings and alerts on the same day.

The AA said it only takes water 11.8in deep to float a car yet more than a third of nearly 20,000 AA members polled said they would have no qualms about driving through this level of water.

As many as 8% would be happy to drive through water as deep as one metre (more than 39 inches).

John Seymour, national manager of the AA's flood rescue team, said: "In the Christmas dash, it's understandable that sometimes people's minds are elsewhere but no one wants to be writing a last-minute letter to Father Christmas after wrecking their car in flood water."