Storm Austen has left thousands without power after 80mph winds hit parts of the UK.
National Grid reported that 9,000 homes and businesses in Cornwall were without power at 9am on Friday after the first named storm of the season reached south-west England.
The west of the county, which has 3,000 registered vulnerable customers, is most affected.
An amber warning for wind, covering Cornwall, Devon and the Isles of Scilly, came into effect at 1am and will remain in place until 10am.
Some schools in the area have delayed their opening until then on Friday as a result. Meanwhile, all schools in Jersey and Guernsey have closed, with roads on the islands blocked by fallen trees and flooding.
Strong winds will be combined with spells of heavy rain, although gusts will gradually ease during Friday.
Forecasters warned of gusts of up to 80mph in parts of the South West, with the highest wind speed, of 74mph, at St Mary’s airport on the Isles of Scilly on Friday morning.
Great Western Railway has imposed speed limits on routes between Devon and Cornwall until 1pm on Friday to keep trains running safely.
The Met Office said Storm Austen was “likely to bring some disruption and possible damaging winds”, warning of problems on the roads and public transport.
Exeter airport has already started to cancel flights. A flight due to arrive from Jersey at 11.10am and another from Edinburgh at 12.50pm have been cancelled, with departures to those locations also halted.
On Friday morning, footage showed high winds battering areas across the south coast. Large waves were seen crashing against Brighton Marina, while trees were battered by winds in the Cornish town of Hayle.
Meanwhile, the Isles of Scilly Steamship Group said its vessels would not be travelling between Penzance and the islands on Friday and Saturday.
The Met Office said flying debris was likely, and that the storm would probably cause some damage to buildings, such as tiles blown from roofs.
Large waves could pose a danger to life, as well as beach debris being thrown onto coastal roads, sea fronts and properties.
Mobile phone coverage and the power supply could also be affected. However, the storm is set to clear into the North Sea by Friday morning.
Network Rail Scotland said trains would be slowed down on Friday and at the weekend to keep people safe in the areas expected to see the heaviest rain.
National Rail said a number of services in the North of England would be changed throughout the day on Friday, advising passengers to plan ahead.
Some services between Leeds and York via Harrogate will not stop at Weeton or Headingley, while trains between York and Blackpool North will skip New Pudsey.
Over the weekend, Storm Boelo will affect Northern Ireland, Scotland and parts of northern England with what the Met Office described as “impactful winds”.
Yellow weather warnings have been issued for the whole of mainland Scotland, the Western Isles, Orkney and the far north of England from 6pm on Saturday to 9pm on Sunday.
There will be “widespread gusts” of 55-65mph, reaching up to 70-80mph in more exposed coastal locations, the Met Office added.
A separate yellow warning, covering Northern Ireland from 6pm on Saturday to 3pm on Sunday, is due to predicted winds of 50-60mph, with up to 65-75mph in exposed regions.
Chris Bulmer, the deputy chief forecaster at the Met Office, said: “The strong winds will be accompanied by heavy rain, making for an impactful weekend of weather.
“Severe weather warnings and forecast detail will continue to develop, so people should keep up to date with the forecast over the next few days.”
Neil Armstrong, the chief forecaster at the Met Office, said: “This is the first stormy weather in the south of the UK this season, and we expect some disruption as it moves through.
“With trees in leaf, it is likely fallen branches and trees could obstruct roads and railways, so take extra care on the Friday morning commute.”