Overnight temperatures will fall to -9 'and even lower' in some isolated areas.
That is according to Met Éireann Meteorologist Joanna Donnelly, who was speaking as two weather warnings are in place for cold conditions.
A status orange low temperature/ice warning is in place for Carlow, Kildare, Kilkenny, Laois, Longford, Louth, Meath, Offaly, Westmeath, Cavan, Monaghan, Clare, Cork, Kerry, Limerick, Tipperary, Galway, Leitrim and Roscommon.
While a status yellow low temperature/ice warning remains in place for the entire country.
Very cold tonight with widespread frost & ice❄️.
Generally clear and dry, though there will be a few showers in the N & NW, falling as sleet/snow🌨️ at times.
Lows📉🌡️ falling below -5°C widely, reaching -8 or -9°C🥶 in some Midland areas by Thursday morning. pic.twitter.com/rvHsrqIwyw
— Met Éireann (@MetEireann) December 14, 2022
Joanna told The Hard Shoulder: "Orange means we're going below -5°, and well below -5°," she said.
"Widely it will be -8°, -9° [and] even lower in local, isolated spots - so a very, very cold night."
She said coastal areas will be the warmest.
"It's away from Dublin, away from the coasts; all the coastal areas, the sea is still relatively warm this time of year," she said.
"So the coastal areas are keeping up around 1° or 2°, just below freezing.
"Inland, anywhere inland at all, is going to be very, very cold tonight and tomorrow night.
"Two very cold nights ahead".
'A change from Sunday'
Joanna said things should change from Sunday.
"Friday still going to be cold, Saturday still going to be cold - we see something of a change from Sunday on," she said.
"There's a southerly wind going to pick up on Saturday night.
"Now it doesn't come without a cost, of course, it comes with wind and rain - that's the change of air mass.
"Certainly a rise in temperatures, just a much warmer southerly airflow... for Sunday and into Monday.
"It's actually going to get cold again after that but not quite as cold as what we're looking at at the moment," she added.