Met Éireann has issued a Status Yellow weather warning for all counties with freezing temperatures forecast tonight.
The national low temperature and ice warning will see the mercury drop to minus three or four degrees tonight.
This will lead to a widespread hard ground frost and icy surfaces, with potentially dangerous conditions, the forecaster warned.
Temperatures will be lower inland and away from coasts.
The advisory will take effect at 6pm tonight and last until 10am on Sunday morning.
Met Éireann says frost and ice on untreated surfaces will be slow to clear tomorrow.
The day will be dry in many areas with good sunshine, with scattered showers near coasts.
It will be "bitterly cold throughout the day" with highest temperatures of just two to four degrees expected.
Status Yellow - Low Temperature/Ice warning for Irelandhttps://t.co/Xg3aMJlyuS
Temperatures will fall to minus 3 or 4 degrees tonight, colder locally away from coasts. This will lead to a widespread hard ground frost and icy surfaces, with potentially dangerous conditions. pic.twitter.com/3zlIcPfOdr
— Met Éireann (@MetEireann) January 2, 2021
Meanwhile in the UK, forecasters say people in parts of northern England, the Midlands and Wales could experience "tricky travel conditions" due to possible snow and ice.
Up to five centimetres - or almost two inches - could fall in some areas.
Britain's Met Office also has a Status Yellow weather warning in place until 6pm.
Experts are warning there could also be injuries from slips and falls on icy surfaces.