Snow showers brought some disruption to high-ground routes like the Glenshane Pass overnight and on Thursday morning.
The Met Office is warning of similar conditions as temperatures fall several degrees below freezing in the coming nights.
A warning for ice has been issued from 4 pm Thursday until 12 noon on Saturday.
This is for counties Derry, Tyrone, Antrim and Down.
A sharp frost is forecast for most inland areas tonight with temperatures likely to fall several degrees below freezing.
Some countryside areas could fall as low as -4C to -5C.
Although many places will stay dry with some sunshine in the coming days, a few showers are forecast and some could be wintry, but mainly over higher ground.
In the Republic, a series of warnings have also been issued including for snow and ice for counties Donegal, Dublin, and Wicklow on Thursday night.
An ice warning had previously been issued by the Met Office for the North of Ireland, from 5 pm on Wednesday until 6 pm on Thursday, for some treacherous conditions.