A status yellow fog warning is in place for five counties.
Met Éireann has issued the warning for Dublin, Kildare, Louth, Meath and Wicklow.
The forecaster said areas of dense fog and freezing fog could affect visibility and create hazardous travelling conditions.
The warning is in place until 10am.
Meanwhile, all of Northern Ireland is under a status yellow snow and ice warning until 11am on Saturday.
The UK Met Office said icy patches and some hill snow were expected in the area on Friday night and Saturday morning.
