A rare "danger to life' warning was issued for impending Storm Eunice as most of Britain was told to “stay indoors" while two weather fronts batter the country in quick succession.
The red warning is for the south-west where potentially lethal 145kph winds are expected to hit the coastline, and gusts of up to 160kph threaten a large swathe of southern England.
Storm Dudley left thousands without power in northern England and Scotland on Wednesday. The Met Office on Thursday first issued amber warnings for most of England, and then upgraded Devon, Cornwall and parts of south Wales to the red warning.
The strongest winds are forecast for southern England but there could also be 145kph gusts in south-west England and south Wales. Wind warnings are also in place for northern England and Scotland.
"It is the most powerful storm we have seen in recent years and we should tie down anything loose," the Met Office's Aidan McGivern said.
Katharine Smith, flood duty manager at the Environment Agency, said: “Strong winds could bring coastal flooding to parts of the west, south-west and south coast of England, as well as the tidal River Severn, through the early hours of Friday morning and into the early afternoon.
“This is due to Storm Eunice resulting in high waves and potential storm surge coinciding with the start of a period of spring tides.”
She said agency teams were making preparations, erecting barriers and clearing screens where flood debris can build up.
Train customers for journeys between York and Leeds and London King's Cross have been told not to travel on Friday when the worst of the winds will bring disruption.
Damage to overhead electric wires in Carlisle means all lines towards Glasgow and Edinburgh were blocked on Thursday.
ScotRail wound down most services from 4pm on Wednesday over fears of falling trees and debris.
Ferries in Scotland have also been severely disrupted, with 20 of the 29 routes experiencing cancellations.
As Storm Dudley moved in on Wednesday afternoon, Capel Curig in Wales was hit by gusts of up to 144kph, with 119kph winds in Emley Moore, Yorkshire and 114kph gales in Drumalbin, Scotland.
Social media users shared images and videos of fallen trees, large waves crashing on to coastal areas, howling winds, sweeping rain, and dark and gloomy skies, as the weather caused havoc to public transport.
One person spoke of seeing a trampoline on a train track, while others posted pictures of unusual cloud formations.
“There's obviously been a generally blustery picture across the country with a combination of rain and hill snow in the north,” Met Office forecaster Marco Petagna said.
Electricity North-West said power cuts were affecting nearly 1,700 homes in Wigan and thousands more around Lancashire.