About 800 homes and businesses remain without power as a result of the high winds and adverse weather brought by Storm Brendan, Northern Ireland Electricity (NIE) has said.
A yellow weather warning for Northern Ireland is in place.
The Met Office said it is in effect until midnight.
NIE said that it had restored power to about 9,500 customers. The worst affected areas were counties Down and Antrim.
NIE said the storm had caused a "low level of damage" to the electricity network.
A spokesman added that teams have been out all day working to repair any damage caused and restore power as quickly as possible.
A number of flights and ferry sailings were also cancelled.
Part of sea wall down in Carrickfergus. Avoid at all costs - police now closing the coast road - very treacherous pic.twitter.com/79kVPjV5i6— Sara Girvin (@SaraGirvin) January 13, 2020
Met Éireann has warned of "several hours of very dangerous weather".
The highest wind gust recorded in the Republic of Ireland so far was 83mph (134km/h) at Roches Point on the County Cork coast and in NI it was 63mph (101km/h) at Magilligan.
Across the Republic of Ireland, more than 48,000 customers were left without power.
About 9,000 remained without electricity on Monday night.
The worst affected areas have been Cork, Kerry, Galway and Mayo.
Still stormy across west & northwest coasts for a time with severe gusts and the risk of coastal flooding. Winds will be mostly fresh to strong southwest winds elsewhere. Scattered squally showers continuing, with further hail & thunder, possibly turning wintry on higher ground. pic.twitter.com/ZS1TYMgV93— Met Éireann (@MetEireann) January 13, 2020
Sea wall collapsed
Travel has also been affected with road closures due to the weather.
The PSNI said Seaview in Warrenpoint and the South Promenade in Newcastle are closed in both directions, due to the adverse weather conditions.
The Belfast Road, Carrickfergus was closed at the junctions with Sloefield Road and Albert Road, as part of the sea wall has collapsed.
Motorists were advised to avoid the area and seek alternative main routes for their journey.
A tree fell on the train line near Seahill station, disrupting travel for a time on Monday. Translink said staff worked quickly to remove it.
Derry City and Strabane District Council closed all its open spaces and play parks on Monday due to adverse weather conditions.
"The public are asked to avoid these areas due to the high winds," a council spokeswoman said.
She added: "The council is urging the public to stay safe by taking the necessary precautions to secure their properties following the Storm Brendan Met Office Weather Warning that has been issued for the region."
Meanwhile, the city's Strand Road, one of Derry's busiest dual carriageways, was down to one lane in the direction of the city centre due to a fallen tree.
The storm was named on Saturday by Met Éireann.
The north coast was also battered by the storm and it was very blustery inland.
Ferry operator P&O cancelled its 10:30, 13:30 and 16:30 sailings from Larne and Cairnryan.
#POLarne / #POCairnryan: we're sorry to advise that due to adverse weather conditions the 16:30 departures from Larne and Cairnryan have now been cancelled. Our next departures are at 20:00. We apologise for the inconvenience caused— P&O Ferries Updates (@POferriesupdate) January 13, 2020
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