More than 44,000 homes and businesses in Northern Ireland have been left without power after the region was battered by snow, sleet and storm force winds overnight.
The damage to the network was concentrated in south and eastern areas, and also parts of the North Coast, operator Northern Ireland Electricity (NIE) said.
George Best Belfast City Airport has reopened its runway after being earlier forced to close due to the weather, while flights at Belfast International Airport have also been disrupted.
More than 70 schools in the region have been forced to shut for the day while commuters have faced hazardous conditions on the roads.
The Roads Service said more than 300 staff in 130 gritters were on stand-by to salt main roads last night.
"Most routes have been salted three times overnight with snow ploughing necessary on many routes," a spokesman said.
Snow drifts of up to 40cm have been reported.
Northern Ireland's World Cup football qualifying fixture against Russia tonight is also in doubt.
Kick-off is due to take place at 7.45pm.
The Irish Football Association said a decision would be made after a pitch inspection and assessment of the South Belfast stadium later today.
If the match does not go ahead tonight, the IFA is looking at the possibility of playing it tomorrow.
NIE said hundreds of additional engineers had been deployed to deal with the effects of the 55 mph winds and snow.
A spokeswoman for NIE said power lines had been hit by flying debris and affected by lying snow.
"Right across Northern Ireland the high winds and snow in the east have affected electricity supplies," she said.
"We have quite a few faults on our high-voltage network and that is affecting the highest volume of customers.
"We will be doing our level best to restore all faults as quickly as possible."
Phone lines and electricity supplies were down for a time at the Mater Hospital in North Belfast.
Wallace High School in Lisburn, Methodist College in Belfast, St Kieran's Nursery School in Poleglass, Ashgrove Nursery School in Newtownabbey, Assumption Grammar School in Ballynahinch, Harmony Hill Primary School in Lisburn, Antrim Grammar School, Moorfields Primary School in Ballymena and Fair Hill PS in Kinallen are among the schools that have been closed for the day.
Sean Penston, weather forecaster with MeteoGroup, the weather division of the Press Association, said most parts of Northern Ireland would see snowfall today with the wintry blast due to continue throughout the weekend.