A status yellow low temperature and ice warning is in place.
The lowest temperatures of the year were recorded last night, dropping to at least minus-seven degrees in places.
A status yellow low temperature and ice warning will remain in place countrywide until 12 o'clock this afternoon.
Met Éireann is warning of treacherous conditions on the roads, with severe frost and freezing fog.
Offaly's Cathal Nolan, from Ireland's Weather Channel, says it was extremely chilly overnight: