Drivers are being urged to take extra care as road conditions are described as being extremely hazardous in some areas.
A widespread sharp to severe ground frost has led to icy stretches on untreated roads.
AA Roadwatch has said particular care is needed through counties Meath, Westmeath, Laois, Offaly, Tipperary and Kilkenny.
Road conditions are also very icy in west Clare.
Temperatures of -4C are forecast tonight along with widespread sharp to severe ground frost.
However, the cold spell is not expected to last beyond this weekend.
Elsewhere, heavy snow in Scotland forced the temporary closure of Edinburgh Airport this morning after 10cm of snow was cleared from the runway.
Glasgow and Aberdeen airports did not report any disruption.
