Many parts of the country have been affected by severe frost and freezing fog overnight, with many roads deemed dangerous.
Black ice has left many secondary roads in Leinster and Munster in a very hazardous condition, while dense fog has resulted in reduced visibility across most of the midlands.
The AA are urging motorists to be cautious in areas of Leinster: Dublin, Kildare, Louth, Meath, Wexford and Wicklow.
In Munster, icy conditions are being experienced in Tipperary on secondary routes, severe black ice in Clare and the Conor Pass is closed due to ice in Kerry.
In Connaught, icy conditions are being reported on the Roscommon and Leitrim.
In Offaly, Westmeath and Longford roads have been assessed as treacherous.
Warnings of black ice in Donegal are widespread.
In Cavan motorists are being warned that roads are icy in east Cavan.
The Clones area of Monaghan is said to be icy.
Meanwhile, local authorities in Dublin city and county say overnight public water supply restrictions will remain in place.
The situation will be reviewed tomorrow.
