Motorists are advised a 'yellow alert' - low temperature warning - will remain in place until tomorrow morning.
Temperatures dropped to as low as minus 4 degrees last tonight, but lows of minus 6 are predicted later tonight.
The yellow alert began at 9pm on Saturday and is expected to continue until 10am on Monday.
Road conditions across the northwest made for dangerous travel.
There were a number of incidents in the Rosses area.
The condition of minor roads in the area are described as "dangerous" with particular care being advised on the glen road between Loughanure and Annagry that branches off the main N56. Motorists travelling to Loughanure from Annagry are advised that the crossroads junction in Loughanure is extremely slippy with cars sliding on the the main N56.
An articulated lorry has gone off the road at Crónasealg just outside Dungloe, while cars are reported off at lower Loughanure and in the wider Dungloe area.
The driver of the artic lorry was treated at the scene in the early hours for shock and minor injuries.