More than 17,000 people have lost power supplies and waves of 52ft have already been recorded as a "weather bomb" begins to hit the country.
Freezing winds are expected to peak on Wednesday afternoon, but the first phase of the storm and its effects are being felt.
Engineers are working to restore supplies after power went out in the Western Isles of Scotland just before 7am this morning.
Off the coast of Orkney, a rescue operation was launched to help a British-registered fishing vessel which issued a Mayday call after getting into difficulties.
The 33ft trawler, with 16 Spanish crew, had one of its bridge windows smashed and some equipment damaged in the stormy conditions.
The O'Genita is being escorted to Westray in Orkney by the Stromness lifeboat.
And 20 vehicles had to be freed after becoming stuck in icy conditions on Cairn O' Mount, a high mountain pass, in Aberdeenshire.
The extreme conditions are being caused by rapid cyclogenisis - known colloquially as a "weather bomb" - a deep low pressure system moving slowly eastwards between Scotland and Iceland.
Forecasters have issued widespread weather warnings across Britain, with major travel disruption expected as winds of up to 80mph strike some areas and huge waves hit northern coastal regions.
Waves 52ft high - measured as "phenomenal" on the Douglas Sea Scale - have been recorded off the Outer Hebrides.
Several ferry and train services have been cancelled in Scotland while some bridges have been closed due to high winds.
Schools and nurseries in the Western Isles have been closed.
The Met Office has issued amber "be prepared" weather alerts for western Scotland, the Highlands, Northern Ireland, Orkney and Shetland and Strathclyde regions.
Yellow weather warnings have also been issued across England's South East, South West, North East, North West, Yorkshire and Humber, as well as in northern Wales and several other areas.
More southerly areas of the UK are likely to be hit by a second storm due to roll in from the Atlantic on Thursday night.
