Tonight could be the coldest night of the year.
A Status Orange low temperature/ice warning is due to come into force for 19 countries at 6pm this evening.
It will remain in place until noon tomorrow.
Meanwhile, Status Yellow warning for ice and low temperatures remains in place over the whole country until Friday.
Met Éireann says widespread frost and icy conditions will persist through the rest of the week with any showers potentially falling as sleet or snow.
Alan O’Reilly from Carlow Weather told Newstalk that temperatures will plunge again tonight.
“I think tonight could see the lowest temperatures of this cold spell with temperatures dropping below -8C," he said.
“We could see -9C or even -10C locally in the midlands especially.”
He said things could get a bit warmer over the weekend.
“Certainly, it does look like there will be a - brief at least - milder spell of weather,” he said.
“Wet and windy at times on Sunday, which will see a rise in temperatures across much of the country.”
Mr O’Reilly said it is too early to tell whether we are looking at a white Christmas.
“It is very tricky to forecast that far out,” he said.
“It is looking likely we will see a few more cold days before we head into Christmas Eve but that is just a little bit beyond the reliable timeframe at the moment.”
Met Éireann says there will be snow across Ulster on Thursday night; however, most other areas will stay dry.
Patches of freezing fog may develop as winds drop off.
Road users are advised to take extra care in foggy conditions.
Meanwhile, Irish Water is asking people to conserve water during the cold snap.