Motorists are being urged to drive with extra care today with freezing fog and severe frost in many areas.
The cold snap is set to continue with Met Éireann predicting that temperatures could fall as low as -6C tonight.
Most main roads have been treated and are passable but extreme care is needed on minor roads.
Bus Eireann is also experiencing disruption and delays on services in Limerick and Kerry.
Meanwhile, the Road Safety Authority estimates that around 20 people could be killed over the two-week Christmas period.