More than 1,000 homes and businesses across Northern Ireland are without electricity as a result of Storm Callum.
Dozens of flights have been cancelled at Belfast City and Dublin Airports on Friday morning.
There are also reports of fallen trees blocking roads.
The storm will bring rain and severe gales to parts of Ireland, with the strongest gusts expected in coastal areas.
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 twelve 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.
Fallen trees are 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 come down on the road at Windsor Avenue in South Belfast.
Most FlyBe flights travelling to and from Belfast City Airport between 06:00 and 09:30 BST have been cancelled.
Stena Line has said that the adverse weather has 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”.
Trains will be subject to speed restrictions on Friday morning.
The worst of the wind is expected to last well into Friday morning’s rush-hour commute.
Weather warnings are in place across Ireland as the low pressure systems move north, just to the west of the island.
An amber warning for heavy rain has been issued for most of south Wales on Friday.
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 (96km/h) are expected along the east coast during the early hours of Friday, before winds slowly begin to ease.
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”.
More than 25 Aer Lingus flights travelling to and from Dublin airport have already been cancelled.
Gusts along the west coast could be in excess of 80mph.
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.
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