Information supplied by Met Éireann
Cold and frosty at first today with fog and freezing fog in many places, and some icy patches also.
The frost and fog will clear most parts this morning to give a dry day with sunny spells, however, there is a risk of some fog persisting in a few inland areas all day.
Highest temperatures of 3 to 6 degrees for much of the country, but lingering close to zero where fog prevails.
A little milder in the south and east, with temperatures climbing to between 7 to 10 degrees, especially near the coast, aided by the moderate northeasterly breezes.
Tonight will be cold again in many places with a sharp to severe frost in much of Connacht, Ulster and north Leinster with some freezing fog in places and lowest temperatures of -2 to -6 degrees Celsius.
Not quite as cold in Munster and south Leinster, but there will still be frost and some fog with lows of 0 to -2 degrees inland.
However temperatures will hold at +2 to 6 degrees in coastal fringes of the south and east.
Low temperature warning for Donegal and Mayo; Fog warning for Connacht, Cavan, Monaghan and Donegal; and Low temperature warning for much of Connacht, Ulster and midland counties of Leinster and Munster.
All in place until 10.00am Friday.