A yellow warning for ice has been extended by Met office forecasters and now remains in place until 11am on Thursday, with drivers advised to exercise extreme caution on the roads.
Roads where snow may still be lying and could re-freeze will be worst affected.
"In addition, sleet and snow showers will affect parts of Antrim and Down - with 1-2cm of fresh snow in places, mainly over the higher ground," forecasters advised.
Salting operations carried out by Roads Service are continuing on main routes and are due to be completed by 10pm.
Meanwhile, the B27 Moyad Roiad in Kilkeel remains closed at Spelga, between Kinnahalla Road and Attical Road due to snow.
Flood warnings are in place in the Green Road/Bangor Road area, with melt water from recent snow expected to remain for some time, although the affected roads are passable with care.
But more heavy rain is on the way for Northern Ireland throughout the week.
A yellow alert is in place for Friday, with the Met Office warning that rain "falling on saturated ground, and combined with melting of a deep snow cover on higher ground, brings an enhanced risk of flooding".