Motorists have been urged to exercise caution on the roads today after icy conditions returned to many parts of the country.
Gardaí and the PSNI issued warnings for motorists to take extreme caution as icy conditions made driving difficult.
AA Roadwatch said icy patches have made roads particularly hazardous in parts of Cos Meath, Longford, Limerick, Kerry, Tipperary, Laois, Offaly, Westmeath, Monaghan, Louth, Donegal and Sligo.
The National Roads Authority said it has 50,000 tonnes of salt in stock to treat roads.
Met Éireann said wintry showers will become confined to coastal counties in the north and west tonight, with clear spells elsewhere. It said westerly winds will ease and widespread sharp to severe ground frost will set in. Lowest temperatures of -4 degrees are expected, with ice on untreated surfaces.
It said frost and ice will clear slowly tomorrow and the day will be mainly dry with sunny spells and highest temperatures of 4 to 8 degrees.
South Leinster and parts of Munster experienced snowfalls last night.
In Northern Ireland, drivers woke up to icy conditions and some snow on higher ground today following overnight sub-zero temperatures.
A small-craft warning was also issued as northeasterly winds reached force 6 at times on coastal waters from Carnsore Point to Roche's Point to Loop Head.
Water restrictions are to remain in place in Dublin this weekend, but storage levels in the capital's reservoirs are improving.
Dublin City Council said yesterday that it will review water supplies on Monday and may begin to lift restrictions. It said a full picture of the supply situation will not be apparent until the middle of next week once schools and colleges have returned from the Christmas break.
Night-time water restrictions were lifted entirely earlier this week in Cork city, Kerry, Limerick city and county, Leitrim, Mayo and Donegal.
However, thousands of residents on the east side of Galway will have no water this weekend, or have a disrupted supply. Galway City Council says it is attempting to increase reservoir levels by restricting supply between 10pm and 7am.
Galway County Council said some farms south of Ballinasloe are affected due to leaks in the Kiltormer and Laurencetown areas.
The Northern Ireland Met Office reported that December was the coldest month on record. A new low of -18.7 degrees was recorded by the Met Office station in Castlederg, Co Tyrone, where the record was broken twice in the four days just before Christmas.
The same station recorded a continuous sub-zero spell of 211 hours lasting from December 17th until St Stephen's Day.