Gusts of up to 100mph are predicted to hit the high grounds of Scotland as Storm Abigail batters Britain.
Wind speeds of 84mph have been registered in the Outer Hebrides, and heavy showers, hail and thunder are expected across the country today.
The storm is expected to bring strong winds and heavy rain across Wales and northern England this morning, with the Met Office warning surface water and gusts could cause problems during rush hour.
A Met Office spokesman also warned of snow in some areas of Scotland, and said it will feel much colder compared to the "exceptionally mild conditions we have been experiencing".
All schools in Shetland and the Western Isles are closed to pupils today.
The Met Office has amber "be prepared" warnings in place for rain and wind in the north west of Scotland, while yellow "be aware" warnings cover much of the rest of Scotland.
A number of CalMac ferry sailings have already been cancelled and commuters on the trains and roads are facing disruption.
Western Isles Council said every school and nursery in its area will be closed to pupils, but will be open for teaching staff from 10am.
Shetland Islands Council also announced that its schools will be shut to pupils due to the forecast of strong winds and the possibility of lightning strikes.
Orkney Islands Council said any decision on school closures would be taken this morning.
The closures come amid Met Office warnings of likely gusts of 70-80mph, potentially reaching up to 100mph across exposed locations in the north west of Scotland.
The storm, which is expected to reach its height overnight, has already brought strengthening winds and heavy rain to many parts of Scotland.
By 5pm, CalMac said 24 of its 26 ferry routes were disrupted.
The firm has urged travellers to "think carefully" if they are planning to visit the west coast.
Train operator ScotRail said there is minor disruption on its routes from Glasgow to Carlisle/Newcastle, Glasgow to Ardrossan/Ayr/Largs and Kilmarnock to Ayr.
The Forth Road Bridge has been closed to high-sided vehicles, cars with trailers, caravans, motorcycles, bicycles and pedestrians.
High wind warnings are in place for key crossings, including the Erskine and Kessock bridges, while warnings of surface water have been issued for key commuter routes the M90 and M74.
Dublin Airport said it was experiencing some minor disruption to flight schedules due to strong winds, and advised passengers intending to travel this morning to check online for the latest flight information.
Meanwhile, Dumfries and Galloway Police said there were a number of trees down across the region.
And the Scottish Environment Protection Agency has flood alerts and warnings in place for Dumfries and Galloway, Argyll and Bute, Ayrshire and Arran, Skye and Lochaber, and Speyside.
Met Office meteorologist Emma Sharples said: "The main centre of the low pressure system around which all the winds are going to be strongest is moving from the Atlantic towards the north west parts of Scotland at the moment. That's going to continue to edge towards us.
"There's obviously rain already setting in and winds strengthening across the country and that will continue to be the case through the rest of this evening, with the band of rain spreading eastwards across Scotland and then the wind turning from a south westerly to more of a westerly as we go through towards midnight."
Ms Sharples said the Western Isles had already seen gusts of 55mph and upwards by mid-afternoon on Thursday.
Members of the public have been asked to secure any loose debris, while builders have been advised to secure scaffolding and any loose items on building sites.
People are also being asked to look out for the elderly and vulnerable.
The Scottish Fire and Rescue Service has urged people to take extra care if they are using candles during any power cuts.
Scottish Hydro Electric Power Distribution said it has moved to "yellow alert" and had more than 500 engineers in place in advance of the storm hitting.
The Met Office amber alert - which affects the Outer Hebrides, Highlands and Orkney and Shetland, warns: "Winds will begin to decrease across the Western Isles and the mainland on Friday morning.
"The strongest winds over the Northern Isles will occur on Friday morning before becoming less strong on Friday afternoon."
The storm is the first such weather system affecting the country to merit a name as part of the Met Office ''name our storms'' project, which asked the public to suggest names.
Officials hope the project will help raise awareness of severe weather and ensure greater safety of the public.