Met Eireann has issued a status yellow fog warning for Donegal tonight, along with 12 other counties.
There will be “dense fog in places,” leading to hazardous driving conditions.
The alert will be in place from just after midnight on Tuesday morning until 10am on Tuesday morning.
There will also be a risk of frost tonight as temperatures drop to -1C.
Met Eireann said: “Tonight will be a dry and generally clear night with the risk of frost developing in sheltered places. Mist and fog will form overnight becoming dense in pockets towards dawn.”