A Status Yellow Ice warning will remain in place for the entire country until 11 am this morning.
Met Éireann said temperatures would fall to -3C or -4C in many areas overnight and stay below freezing until mid-morning.
TODAY
Very cold and frosty with icy patches and fog clearing slowly during the morning to give dry and bright conditions with sunshine for a time.
It will be cloudier in northern and western areas.
Highest temperatures ranging from 3C or 4C in parts of Ulster and 7C or 8C in Munster.
Light southerly breezes – becoming fresh near west and northwest coasts.
TONIGHT
Dry and cold in many areas tonight with sharp frost, fog and some icy patches in overnight lows of -2C and 2C.
However, there will be a good deal of cloud with a southerly breeze in parts of the west and northwest which will keep temperatures around 3C to 5C and frost to a minimum there.
