In Belfast and across the North drivers abandoned their cars and walked home as roads became impassable and traffic ground to a halt.
Travel has been severely disrupted by the worst snowfall in two decades.
On Wednesday evening up to seven inches of snow fell, the heaviest since 1983. This was followed by overnight temperatures as low as minus 12 degrees. Steep routes out of Belfast, such as the Saintfield Road to the east, were littered with abandoned vehicles.
On the M2 motorway a sliproad was blocked by a lorry, and other roads such as the Hillsborough bypass on the main Belfast-Dublin road were also temporarily closed. By yesterday morning most main roads were passable, albeit with care. Journeys took more than twice as long as normal with drivers mostly staying below 30 m.p.h. even on motorways.
The M1 motorway into Belfast was reduced to one lane for much of the day. By late afternoon both lanes were usable, but freezing fog became increasingly widespread from mid-afternoon.
Elsewhere, the Glenshane Pass on the main Derry-Belfast road was open, as were roads to Enniskillen and Omagh. In Armagh routes to and from Armagh city and Portadown were usable, again with care.
The RUC said side roads everywhere remained untreated throughout the day and advised drivers to venture out only if it was absolutely necessary.
Public transport was also affected. Most trains were 20 minutes late, and a spokeswoman for Translink said buses were not running to their timetables. What bus services there were finished early, and many shops closed ahead of time to let staff get home.
Taxis were scarce also. The airports were open and accessible by road for most of yesterday, but closed runways at many British destinations meant they soon became crowded as flights were cancelled or delayed. By 6 p.m. Belfast City Airport was still open, but those at Aldergrove and Derry had closed.
The cold weather also had an adverse effect on health services. The Northern Ireland Ambulance Service put special measures in place to ensure its emergency services kept running. The Minister for Regional Development, who is responsible for roads, rejected criticism that his department had not reacted to weather warnings early enough.
Mr Gregory Campbell said that personnel operating 120 gritters had been out all day on Wednesday and had worked all night. "Unfortunately in many areas soon after a road was cleared the heavy snow made conditions difficult again for motorists," he said.
More snow showers and temperatures as low as minus 15 degrees were being forecast last night.