A status yellow freezing fog warning has been issued for 19 counties.
It's in place in Munster, Galway, Roscommon, Carlow, Dublin, Kildare, Kilkenny, Laois, Longford, Meath, Offaly, Westmeath, Wexford, Wicklow until 4pm.
Met Eireann say patches of fog will persist causing hazardous driving conditions.
The cold snap will continue until at least the middle of next week after Met Eireann extended it's winter weather advisory until Wedesnday.
It's led to calls for the public to check in on older people, and for motorists to slow down.