Motorists and pedestrians are being warned of severe black ice in many parts of the county.
Gardai have already reported a number of accidents after cars left roads across the county.
Although Donegal has not yet been hot by heavy falls of snow which is impacting other parts of the county, some snowfall is expected later in the day.
However, a cold weather warning with plunging temperatures remains in place.
Two cars are off the road at Newtowncunningham and the emergency services are on the scene.
There are also cars off the road outside Donegal Town and in Lifford.
Gardai have advised motorists to exercise extreme caution when driving even if roads appear clear.
