The UK Met Office has warned that "phenomenal" waves more than 45ft high are expected to buffet south-west England, with winds of up to 80mph.
The waves are predicted for 12 miles offshore. Jo Smith from Brixham Coastguard said the inshore forecast was "not looking good, with winds increasing".
She added that local communities would "feel the brunt".
On Saturday, about 670 homes in the Newbury, Basingstoke, Bournemouth and Salisbury areas were without electricity. More than 300 homes in Cornwall also had no power.
Areas most at risk of flooding are Mullion, Newlyn, Looe, Porthleven, Kingsand and Cawsand, Cornwall Council's Silver Command Unit has said.
The Ministry of Defence has put 1,500 personnel on notice to help in southern England if needed.
The recent storms in Cornwall have caused around £14m of damage, according to the local council.
The Met Office issued an amber warning for high winds in south Wales and south-west England and said southern England had seen "one of the most exceptional periods of rainfall in 248 years".
The Conservative MP for Bridgwater and West Somerset, Ian Liddell-Grainger, told the BBC that river levels in his constituency remained "enormously high" and people there were "having to batten down again to prepare for the next storm".
He criticised the Environment Agency and its head, the former Labour cabinet minister Lord Smith, for not dredging in the area to prepare for storms.
"We have been let down by London," he said. "On the ground they [Environment Agency staff] are working hard. Up in London I don't know what they are doing."
The Environment Agency has two severe flood warnings - which mean "danger to life" - in place, both in Somerset.
The agency has also issued more than 190 flood warnings and more than 300 flood alerts.
Despite warnings by coastguards to keep away from the region's beaches, professional windsurfers have travelled to Gwithian, in Cornwall from around the world to ride the waves.
Watch huge waves batter the coast of Britain: