Northern Ireland Electricity (NIE) has said about 1,200 customers are without power after strong winds caused disruption to supplies.
Northern Ireland Electricity (NIE) has said power has been restored to most customers after strong winds caused disruption to supplies.
Overall close to 30,000 customers have been affected at some point, with the highest number off power at any one time about 7,000.
Close to 30,000 customers were affected at one point, with less than 20 still without power.
The Christmas market in Belfast city centre was closed as a safety precaution. It re-opened at 14:00 GMT.
The Christmas market in Belfast city centre was closed as a safety precaution. It re-opened at 14:00 GMT.
The Met Office has also issued a warning of the likelihood of ice.
Several roads were closed due to fallen trees. Ferry and rail services were also disrupted.
Police said several roads have been closed due to fallen trees.
NIE said engineers and emergency crews were working on all "known faults" and hoped to have customers back on supply on Friday morning.
Some ferry services have also been cancelled.
The company brought in teams from other parts of Northern Ireland to help in the restoration process.
NIE said it had opened local incident centres across Northern Ireland.
The firm's spokeswoman Julia Carson said engineers and emergency crews would work "while it is safe to do so".
"Our focus is to have the majority of customers back on supply tonight and we have brought in teams from other parts of Northern Ireland to help in the restoration process.
"However, due to the high volumes of individual faults, some customers in isolated areas may be off supply for a longer period," Ms Carson added.
Strong winds led to the Foyle Bridge being closed to high-sided vehicles earlier on Thursday, but it has now re-opened.
In County Tyrone, the road between Moneymore and Cookstown was closed for a time, after strong winds caused a large milk silo at the Dale Farm plant to break loose from its foundations. It was slightly damaged, but has since been secured.
Disruption
All ferry sailings between Rathlin and Ballycastle have been cancelled because of the weather conditions.
P&O Ferries said it anticipated disruptions on its services from Larne and Cairnryan.
It said anyone travelling on Thursday should check in as normal but expect delays.
The company said its latest sailing information would be updated on its travel information and weatherline on 0845 832 8888.
Northern Ireland Railways said debris on the line had led to delays and cancellations on its Londonderry and Larne services.
John Wylie from the Met Office said: "It's completely normal for the time of year. We've got to expect a few stormy periods every winter."
