Met Éireann has issued a Status Yellow fog warning for much of the country including Clare.
The weather says overnight fog will be dense in places and may lead to hazardous driving conditions. Fog will linger locally during Sunday morning also.
The affected counties include Carlow, Clare, Cork, Dublin, Kerry, Kildare, Kilkenny, Laois, Limerick, Longford, Louth, Meath, Offaly, Tipperary, Waterford, Westmeath, Wexford, and Wicklow.
The warning comes into effect at midnight Saturday and will remain in place until 10.00am on Sunday.
A number of flights were forced to divert to Shannon Airport early on Saturday as a result of dense fog and poor visibility at Cork and Knock airports.