Heavy snowfalls in the east brought commuter traffic in Dublin, Louth and Meath to a complete standstill earlier tonight.
There were lengthy tailbacks on several of the capital's main arteriel routes this evening while traffic on M50 motorway, where a number of trucks had jack-knifed, was described as gridlocked.
Similar traffic disruption was experienced in urban areas across Meath and Louth.
Flight operations were suspended at Dublin airport shortly before 6pm because of the worsening weather. It is not expected to reopen until 11pm. Passengers are strongly advised to consult with their airline before travelling to the airport because of knock-on delays.
All other Irish airports remain open, although many flights out of Ireland were cancelled as a result of snow and ice across Britain and parts of Germany, France, Italy and the Netherlands.
Heathrow, Britain's busiest airport, and Gatwick were closed to all inbound flights while only a handful of departures were allowed. Airports elsewhere in the UK were also affected.
Ryanair has put on a number of extra flights today in an attempt to clear the backlog and Aer Arann has had to cancel a number its services including Knock to Dublin, Sligo to Dublin and Dublin to Sligo.
Temperatures in Ireland are unlikely to rise above freezing for a number of days, but principal roads should remain passable for those seeking to travel in the run-up to Christmas.
However, a heavy snowfall in Dublin brought rush hour traffic across the city to a standstill with long tailbacks developing on the quays and Pearse Street, Tara Street and Gardiner Street.
Luas red line services were only operating between Smithfield and Tallaght Stops due to an incident in the city centre.
AA Roadwatch said motorists driving in Wicklow should avoid Kilgarron Hill, Enniskerry, the Wicklow Gap and Sally Gap.
Met Éireann said conditions would remain very cold up to and including Christmas Eve and that some counties on the east coast may experience snow showers tonight and tomorrow.
Temperatures last night dropped to as low as minus 18 degrees at Castlederg in Co Tyrone and minus 17 degrees in Foxford, Co Mayo.
The cold weather is likely to persist over the coming nights, with temperatures of between minus 10 and 15 forecast to hit the north and northwest regions again tonight.
Local authorities said water supplies had not been seriously depleted despite the recent drop in temperature.
Dublin City Council, which is still restricting night time water supply in some areas, said almost 40 million litres had been conserved over the weekend. It said any restrictions should be lifted by Thursday allowing for normal supply over the Christmas period.
The National Roads Authority (NRA) said salt supplies were at sufficient levels with about 8,000 tonnes in reserve nationally.
The NRA said it takes about 2,000 tonnes to grit principle roads nightly and that a fresh shipment of salt would arrive in Cork on Wednesday. It said some 25,000 tonnes would be available to service roads over the Christmas period.
Local authorities have also made arrangements with the Irish Farmers Association and Irish Creamery Milk Suppliers Association to supply grit to be spread on secondary roads where necessary.
The Garda said people planning to travel over the coming days should use primary routes whenever possible, drive at the appropriate speed and plan journeys in advance.
Pedestrians have been advised to wear high-visibility clothing in poorly lit areas as fog is expected to make driving conditions challenging.
Bus Éireann said the majority of its services were running as normal but that there were cancellations and delays on some routes in effected areas.
Irish Rail said all trains were operating but that frozen points were causing delays on routes through Portlaoise and Limerick Junction.
Cork City Council said no collections of domestic waste would take place today ebcause of the "inclement weather conditions". It said collections for the remainder of the week would be dependent on the weather and that customers would be advised accordingly.
Dún Laoghaire-Rathdown County Council said some homes in the Sandyford and Stepaside would experience low water pressure or be without supply until tomorrow morning because of a broken pump at Sandyford reservoir.
It said water supply would be switched off from 7pm to 7am in the Monkstown, Loughlinstown and Ballybrack areas. Pressure will be reduced in Dundrum, Blackrock, Glenageary, Milltown and Dalkey from 7pm to 7am.
