MOTORISTS were last night warned that the country's roads will be lethal and covered with "sheets of ice" for the next 48 hours.
As the latest Arctic snap hits today, Met Eireann has predicted that ice will make many roads treacherous, with temperatures falling as low as -8C.
Black ice gripped many roads last night and made them very dangerous as snow fell and temperatures plummeted.
Flurries of snow fell in Co Donegal by 7pm, while temperatures dipped quickly in Monaghan, Westmeath, Donegal and Roscommon.
The black ice was expected to be widespread by this morning and affect most areas, according to AA Roadwatch.
Worst affected areas include north Munster, most parts of Leinster, the midlands and the north west.
Gardai advised motorists to take extra care on the back roads around Dundalk last night due to patches of black ice.
Met Eireann forecaster Vincent O'Shea said the very low temperatures would cause serious problems on the roads tonight and tomorrow.
Severe frost will be widespread, while snow will mainly affect the east and south of the country.
"Roads will be very hazardous on Friday into Saturday. There will be dangerous sheets of ice out there," said Mr O'Shea.
Outbreaks of sleet and snow will spread to much of the rest of Leinster, but most of Ulster and Connacht should stay dry, with some brighter spells. Snowfalls of 3cm to 5cm can be expected in the south and east.
AA spokesman Conor Faughnan said the big danger this time would be ice rather than snow on the roads.
"The concern is that the roads may not appear as bad as before when, in fact, there will be ice on the surface, making it desperately dangerous," he said.
"The sun might be on the road and it might look good, but there could be ice in a shady spot.
"The golden rule is -- slow down and stay well away from the car in front. Speed will make any accident much worse."
The big freeze is expected to be shortlived with the last of the rain, sleet and snow clearing from Leinster and Munster tomorrow.
Temperatures will continue to remain low, with westerly breezes adding a wind-chill factor.
The early days of next week will bring milder weather to the country, as the winds turn to a southwesterly direction, and temperatures jump to nine or 10C during the day.
Meanwhile, water restrictions are set to continue in the greater Dublin area until another 100 million of litres of water are added to council reservoirs.
Night-time restrictions have been lifted entirely in Cork city, Kerry, Limerick city and county, Galway city, Leitrim, Mayo and Donegal.
However, some short-term disruptions to supplies will continue in pockets affected by low pressure, and while leaks are being repaired.
The Department of the Environment said the supply situation in Dublin is continuing to improve, with production again exceeding demand yesterday.
The detection of leaks and repairs are also continuing.
Night-time restrictions will be in place on some supplies until treated water-storage levels return to near normal.
A further increase in demand for water is expected when schools nationwide return from their Christmas break on Monday.
However, it is not anticipated that this will cause any further significant disruption, according to the department's statement.
As water supply slowly returns to normal levels in Co Clare, it has been confirmed that up to 20km of old water pipes need to be replaced in Ennis, where over half the town's supply is being lost every day due to leaks.
Householders in a number of areas of Galway city continue to suffer from water problems caused by the severe weather conditions.
Meanwhile, water restrictions will remain in place in parts of the country for at least another week.