Met Éireann said that record low temperatures were seen in parts of the country last night, with some areas seeing temperatures as low as -16degrees.
Sub-zero temperatures are expected to last for a few more days with a thaw not expected until Christmas Eve.
Forecaster Evelyn Cusack said that there will be no thaw until Christmas Day, when rain and southerly winds are more likely.
The weather continues to cause chaos for travellers. The AA has issued road warnings across the country. Dublin Bus and Bus Eireann have confirmed that most services are running as normal but there are some curtailments. Travellers are advised to check their websites – www.dublinbus.ie and www.buseireann.ie – before setting out on their journeys.
Meanwhile, heavy snowfall in Europe is disrupting air traffic.
Irish airports are all open but flights have been affected by conditions in mainland Europe and the UK.
The Dublin Airport Authority has asked all customers to check their airline’s website before coming to the airport.
London airports have been badly affected. Heathrow has reopened this morning but delays and cancellations are expected throughout the day.