Temperatures look set to plunge even further over the next few days.
Met Eireann's severe weather warning remains in place with heavy frost and air temperatures of below -10C expected to continue throughout the weekend.
It is expected to be bitterly cold by Sunday as a strong easterly wind adds a biting wind chill factor.
There is also a risk of further snow showers coming in off the Irish Sea to hit the Dublin and Leinster region over the next few days. On Sunday, there is a more general risk of snow.
Thick freezing fog added to the difficult road conditions yesterday afternoon as commuters began to exit the capital.
Drivers were urged to take extra care as visibility was reduced amid plunging temperatures, particularly in west Dublin and along the M1 and the M50.
AA Roadwatch described conditions throughout Dublin as treacherous by evening time.
Dublin City Council yesterday re-deployed around 500 staff to assist road maintenance crews in removing ice and snow from around the main hospitals in the city.
Most schools across the south-east did not re-open yesterday following the holidays, and many will stay closed today as a result of the dangerous roads in the area.
Overnight snowfalls in Waterford and Wexford left numerous roads in a dangerous condition. Road conditions around Co Kildare and Kilcullen town were described as extremely poor, with freezing fog around Naas, Kildare town and in Monasterevin.
Plunging temperatures resulted in very icy conditions on the N3 in Co Meath.
The N2 was reduced to one lane at Ashbourne, while drivers also had to deal with heavy fog last evening.
Motorists were warned routes around Slane, Trim, Kells, Athboy, Oldcastle and Ratoath were very icy, while in Louth, secondary roads were described as very poor.
Many roads are in a treacherous condition.
Donegal County Council senior engineer, Vincent Lynn confirmed that the council had just 100 tonnes of salt in storage, enough for half a day's salting in normal circumstances.
Sligo Airport, which had managed to remain open since the cold spell began, was forced to close yesterday.
The continuous snow is also causing concern about people, particularly the elderly, who are living in isolated areas.
A convoy of trucks is expected to take 4,000 tonnes of rock salt from Limerick Docks today to local authorities.
Shannon Foynes Port Company said the shipment was expected to arrive in the Mid-West in the early hours.
A thaw prevailed throughout Limerick, Clare and north Tipperary as the afternoon progressed, with no major accidents recorded. However, some routes are said to be extremely treacherous for motorists.
Dense fog was reported around Longford town and on the M6 in the west of Kilbeggan, Co Westmeath, and around Athlone and Mullingar.
Family doctors, district nurses and home helps in several parts of the West are unable to get access to patients because of the road conditions.
Ambulances are unable to make some trips, according to Castlerea-based GP, Dr Greg Kelly. E
ast Galway and parts of Roscommon remained the worst affected areas of the West yesterday. Roads in Boyle, Castlerea, Fairymount and Williamstown were in poor condition, with several stretches affected by black ice.
SOUTH AND SOUTH-WEST
Almost 25 Cork schools remained closed yesterday due to concerns about frozen roads and playgrounds as well as water and heating issues.
Roads around Newmarket, Blarney, Macroom, Mitchelstown and Youghal were reported to be extremely dangerous, while in Kerry, heavy ice was reported in areas around Killarney, Kenmare and Sneem.
Concerned farmers offered to help out Cork Co Council with its road treatment programmes by putting their tractors at their disposal.