A yellow severe weather warning for more snow and ice over parts of Northern Ireland is set to cause further disruption.
Almost 400 schools were closed across the country.
Most out-patient medical clinics in the south of the country were cancelled.
A statement from the Infrastructure Department said staff were working round the clock to clear roads in the south east.
“Conditions extremely difficult in some areas and some abandoned cars blocking roads. Wind leading to drifting in many areas.
“Only travel in this area if essential.”
The Mourne Mountain Rescue Team said it was out from 5am helping essential staff reach Daisy Hill Hospital in Co Down.
“Conditions in the area are treacherous and making it impossible for many staff members to travel.
“Given that Daisy Hill provides a critical service to both the team in our role as well as the wider community, it’s a privilege to be able to help.”
Approximately 40 staff were supported on Thursday night, with the team active up to midnight. A further 40 were supported on Friday morning.
Conditions on the main road from Belfast towards Dublin were poor due to the weather.
Many minor country roads near Moira were impassable due to large drifts.
The Belfast airports were open, but passengers were advised to check with their airlines.