Numerous landslides – damaging roads and railway lines, blocking beaches and ripping out sections of coastpath – have already hit Devon and Cornwall during the recent floods.
The Met Office, which issued the warning following advice from the British Geological Survey, said coastal areas in the region were particular in danger of collapsing cliff edges and rockfalls, but stressed that all areas enduring heavy rain were at risk.
"We have had such heavy and persistent rainfall over the last few days and weeks that there is a danger of landslides and rockfall along the coast, even on coastal paths," a spokesman for the Met Office said.
"We are advising post-Christmas walkers in the South West of England to take particular care in these dangerous conditions, especially those not familiar with the area.
"Do not get too close to the cliff edge or walk under the cliff face along the beach and remember that coastal paths could be impacted too."
The warning was issued just a week after the inquest into the death of Charlotte Blackman who was killed on Freshwater Beach in Dorset when around 400 tonnes of rock crashed down on top of her. The 22-year-old died in the landslide in July.
Many coastal paths in the South West have been closed over the last few weeks and train services have been disrupted by small coastal landslides.
The Environment Agency had 17 flood warnings in place in the region yesterday including on the River Cober at Helston where residents had to be evacuated before Christmas. There were also 55 lesser flood "alerts" in the South West as heavy rains again swept through.
Around 470 properties have flooded since Wednesday, while Floodline revealed it has received 18,000 calls during the recent wet weather.
In Devon and Cornwall 245 properties flooded over the weekend and although a number of people were evacuated, most have now returned home.
In the flood-hit village of Braunton, which was virtually cut off after water topped flood defences, the clean-up has already got under way.
North Devon Council brought in skips and vehicles to transfer rubbish from flooded homes and businesses.
"We want to make it clear that we are here for people throughout the Christmas period," council leader Brian Greenslade said.
"We have staff on standby if the situation deteriorates again throughout the next few days.
"Although things are looking better in terms of the weather, we can't be complacent so we have robust plans in place to cope if the weather takes a turn for the worse."
Heavy rain has continued to keep the emergency services and highways teams busy. On Christmas Eve, a teenager was rescued by members of the public after her car aquaplaned on Par Moor Road, Par, near St Austell.
Police said the 18-year-old driver, whose Honda Civic had overturned into a pool of water a foot deep, was at risk of drowning until passers by intervened.
She was airlifted to Derriford Hospital in Plymouth where she received treatment for minor injuries.
In Cornwall, firefighters helped the owners of a house in Wreford Close, St Columb, to salvage their belongings after it was hit by flooding on Christmas Eve.
The same day, St Austell firefighters were also called out to pump flood water from a house in Station Road, St Blazey. On Christmas morning, firefighters pumped out the flooded basement of a property in Brook Street, Mousehole.
Firefighters in Somerset also had to rescue a man on Christmas Day whose car had become stuck in flood water at Comeytrowe Lane, Taunton.
