Motorists have been urged to exercise caution on the roads today as heavy fog and ice make driving conditions difficult in many areas.
The east, west and midlands are the worst-affected by freezing fog and patches of black ice.
A number of flights into and out of Dublin airport have been delayed. Intending passengers are advised to contact their airline before travelling to the airport.
AA Roadwatch has warned of icy and foggy conditions around Thurles in Co Tipperary and in Monaghan town. Visibility is said to be extremely poor near the M4 toll plaza near Kilcock and on the M6 between Rochfortbridge and Oranmore.
A number of crashes were reported due to ice on the inside northbound lane of the M1 between Dunleer and Castlebellingham, where there have been several minor crashes today.
There is also black ice on the N4 at Carrick-on-Shannon and on the N6 between Athlone and Ballinasloe.
Met Éireann said fog will linger in some areas throughout the day. Otherwise, it will be mostly dry with some sunny spells. The will be some showers across the north and northwest.
Highest temperatures will be 5 to 8 degrees in brighter areas, but only 2 or 3 degrees where fog persists. Winds will be light variable or northwesterly.