Big Freeze to continue until Christmas
Overnight temperatures are to plummet as low as minus 15C in parts this week but Christmas will be dampened by wind and rain from the Atlantic, pushing the thermometer up.
The mercury dropped bitterly low last night, with temperatures at Castlederg, Co Tyrone, falling to a bone-chilling minus 18C.
Motorists have been urged to drive with extreme care as icy conditions persist, but road chiefs said fresh salt shipments would arrive by Wednesday.
Met Eireann said the end is in sight to the Arctic conditions, with temperatures as high as 10C by Christmas Day.
Forecaster Pat Clarke said: "The good news is we are expecting the weather to get milder during Christmas Day.
"What's going to happen is a band of wet and windy weather is going to sweep in from the Atlantic.
"That will bring rain."
Mr Clarke said sleet and snow may fall during Christmas Day as the Atlantic system meets the cold air.
Snow remains a risk in the east coast today and tomorrow as showers linger in the Irish Sea, with parts of Tipperary, Waterford and east Cork also under threat.
Temperatures up until Wednesday night will be as low as minus 15C, particularly in the north west.
The rest of the week is expected to be dry but cold, with overnight restrictions on water in Dublin to be lifted by Thursday.
Christmas week will see temperatures of up to 9C, with cool nights.
The north and west suffered further outbreaks of snow last night, with road conditions described as hazardous around Glenties in Co Donegal and icy across the region on back roads.
Temperatures dropped to minus 18C last night in Co Tyrone, minus 17C in Foxford, Co Mayo, minus 12C in Belfast and minus 11C in Mullingar.
But Mr Clarke said normal night time values would soon be up to 5C.
The National Roads Authority (NRA) said it has 8,000 tonnes of salt left, but 4,000 tonnes are due to arrive on Wednesday and every two days thereafter, bringing reserves up to 25,000 by Christmas week.
Joe Crockett, Kilkenny city and county manager, said while salt stocks are low, the arrangements with the NRA to secure supplies has worked.
"Salt supplies have been scarce. There has to be a strategic framework for the application of salt and we have more salt supplies on the way so the arrangements are working," he said.
Gardai urged people to continue to exercise extreme caution on the roads and to check vulnerable and elderly neighbours or relatives.