A status yellow fog warning is in effect for 17 counties until 10 o'clock this morning.
They include Carlow, Kildare, Kilkenny, Laois, Longford, Meath, Offaly, Westmeath, Cavan, Clare, Limerick, Cork, Tipperary, Waterford, Galway, Leitrim, and Roscommon.
Met Éireann says areas of dense or freezing fog are possible, leading to impaired visibility and hazardous travelling conditions.
The fog will clear gradually, followed by bright or sunny spells and occasional showers.