Care is being urged on the roads today as temperatures are set to hit -8C in some areas.
Hundreds of thousands of people are expected to travel over the next two days in the run up to Christmas Day.
Hazardous conditions such as snow, ice and freezing fog have prompted road safety warnings.
On the N6 Dublin-Galway road at Kilbeggan, it has fallen to -6C. In Roscommon, treacherous road conditions are reported on the Castlerea-Frenchpark road.
Donegal garda are also reporting very icy conditions on roads right across the county, especially on secondary routes.
In Clare, roads around Shannon and Newmarket-on-Fergus are particularly effected.