Storm Callum has swept in, bringing 70mph winds and disruption to travel and power supplies across some parts of the UK and Ireland.
More than 1,000 homes and businesses across Northern Ireland are without electricity.
Dozens of flights have been cancelled at Belfast City and Dublin Airports while Belfast International Airport has warned of potential flight delays.
In Wales winds hit 72mph (116km) and hundreds of homes are without power.
In many areas, the clear-up is already underway.
Fallen trees were blocking the Tassagh Road in Keady in County Armagh and the Scarva Road heading out of Gilford in County Down, while a tree has also came down on the road at Windsor Avenue in South Belfast.
The storm has brought rain and severe gales to parts of Ireland and Wales, with the strongest gusts expected in coastal areas.
How is transport affected?
Most FlyBe flights travelling to and from Belfast City Airport between 06:00 and 09:30 BST have been cancelled.
Belfast International Airport said that while all flights are still scheduled, there may be knock-on delays.
More than 25 Aer Lingus flights travelling to and from Dublin airport have been cancelled.
Stena Line has said that the adverse weather caused a delay to its 07:30 service between Belfast and Cairnryan.
Translink has warned that the punctuality of rail services will “regretfully be adversely affected” while Arriva Trains Wales has put on replacement bus services and cancelled some trains.
Trains are also subject to speed restrictions while the A55 Britannia Bridge between Anglesey and the Welsh mainland has been closed to high-sided vehicles, with one lane shut on the M48 Severn crossing.
But the worst of the wind is expected to have finished after Friday morning’s rush-hour commute.
What’s the forecast?
In Northern Ireland, a yellow warning has been issued by the Met Office for strong winds.
The agency says some delays to road, rail, air and ferry transport are likely because of the storm.
The strongest gusts of more that 60mph are expected to have reached their park on Friday morning, before winds slowly begin to ease.
An amber warning for heavy rain has been issued for most of south Wales on Friday.
In the Republic of Ireland, weather service Met Éireann has issued the second highest level of warning – a Status Orange – for all coastal counties.
The agency warns there is a risk of coastal flooding and damage, especially along the south and west coasts, as the storm coincides with high tides.
The warning also tells people to “stay away from exposed coastal areas for the period of the orange warning”.
Gusts along the west coast could be in excess of 80mph.
What are the power outages?
Northern Ireland Electricity (NIE) says more than 900 homes and businesses in Lisburn, County Antrim, are without power.
A further 150 homes and businesses in Lurgan in County Armagh and Ballinamallard in County Fermanagh are also without electricity.
NIE has opened 12 incident centres across Northern Ireland to respond to any damage to the network.
It has urged people to stay away from fallen overhead power lines and to report any electricity network damage to 03457 643 643.
Storm Callum is the third named storm of the season and follows Storms Bronagh and Ali in September.
During the 2017-18 season, there were 11 named storms.