Severe disruption has been caused to air and road transport by deteriorating weather.
Road temperatures on all national routes are well below zero. The N5 Dublin/Westport Rd at Charlestown is experiencing temperatureas of -5.7°C.
Motorists in many parts of Leinster are advised not to travel, unless absolutely necessary. The warnings also extend to Roscommon and Galway. Secondary routes in all areas are treacherous and should be avoided.
Sean O'Neill from the National Roads Authority is advising motorists to take major routes where possible when travelling as they are being gritted.
He said motorists should also travel in the slow lane as barriers on the east-west motorways are blocking the sunlight and preventing it from melting the ice in the fast lanes.
In Laois, The Mountrath to Clonaslee Rd, known locally as the 'Cut Road' is impassable due to snow and ice. Nearby, the Kinnitty Mountain roads in Co. Offaly are also impassable. There is severe ice on the M7 in both directions around Portlaoise.
In Westmeath the gardaí say conditions are treacherous on the M4 Sligo/Dublin Rd and ramps between Mullingar and J8 Kilcock. It is extremely icy on the M6 between Tyrellspass and Rochfortbridge.
In Carlow it is reported to be very icy on the N80 Portlaoise/Wexford Rd particularly on the outskirts of Carlow town with freezing fog to contend with.
In Meath, conditions in Oldcastle are treacherous. The N3 outside Navan and Kells is icy. There is ice on the N2 between Slane and Ashbourne and on the Ashbourne Bypass.
In Kildare, The M7 is extremely dangerous between J13 Kildare and J9 Naas North. Motorists should travel in the left lane.
In Wexford, conditions in Gorey and Wexford town are extremely slippery. Avoid the Blackwater/Wexford Rd(R741). The N11 around Wexford is treacherous, particularly at Ferrycarrig.
In Wicklow, it is extremely icy on the N11, motorists are urged to use the left lane, as conditions are very icy in the right lane and treacherous in Wicklow town.
Wicklow and Sally Gap is impassable due to snow and ice as is the Glencree area.
In Galway there are very icy conditions throughout the county in Galway city Taylors Hill is treacherous.
All roads around Barna are extremely treacherous due to ice.
There is black ice on the N65 Portumna/Borrisokane Rd and on the Portumna/Birr Rd (R489).
In Mayo there are dangerous driving conditions on the N5 Castlebar/Swinford Rd at Bohola.
Westport, Castlebar and Ballina in particular on secondary routes have very poor driving conditions.
In Sligo it is icy around Ballymote, in particular on the Riverstown and Castlebaldwin Roads.
In Roscommon, roads throughout Castlerea are hazardous and it is also icy on the Boyle/Gorteen Rd.
In Cavan, caution is advised when driving through Bailieborough due to extremely icy roads.
In Cork it is very icy on the Blarney/Ballincollig Rd in Douglas and around Castletreasure.
There are icy conditions around Timoleague,Kilbrittain and also around Midleton.
The Old Youghal Rd is closed between New Rd and Gordon's Hill junction due to icy conditions.
In Limerick there are reports of freezing fog on the N24 Tipperary/Limerick Rd approaching Limerick city, and on the N18 between Limerick and Shannon.
In Kerry, patches of freezing fog around Killarney and on the N21 Castleisland/Abbeyfeale Rd is very slippery.
In Clare, freezing fog has resulted in extremely poor visibilty around Shannon.
In Dublin, the N4 is icy both ways from the SCR junction to the Chapelizod Bypass.
The slip road at J3 Lucan is also very slippery. The Strawberry Beds and Tinkers Hill are impassable due to icy conditions. Hillcrest Rd is extremely icy.
On Bluebell Ave at the junction with Kylemore Rd road conditions are dangerous.
Conditions on Brookfield Rd in Kilmainham are poor. Island Bridge, Chapelizod and Parkgate Street gates are closed into the Phoenix Park due to extremely icy conditions. Knockmaroon Hill is also closed due to ice.
The Raheny Rd is extremely dangerous, particularly at the Hill Top Shopping Centre
Motorists are advised to avoid Tonligee Rd and also the Howth Rd at Sybill Hill.
Gardaí are warning of icy conditions on Griffith Avenue.
There are ice patches on the Malahide and Yellow Walls Rd.
Motorists are advised to continue to drive with extreme care on the M50 southbound from J13 Ballinteer to the M11.
In Newtown Park Avenue getting onto the N11 is impassable due to ice. Motorists have been reporting extremely icy conditions on the N11, in particular northbound at Foxrock.
The AA says Glenageary Rd Lower is impassable due to ice. There are reports of black ice on Seapoint Avenue in Blackrock.
There are extremely poor conditions on Kill Avenue.
Dublin Bus services will not be running on any routes for the remainder of the day due to the road conditions. This includes nitelink services.
All inter-city services from Dublin are now operating, apart from Dublin-Rosslare and Dublin-New Ross which are not operating. Dublin-Clonmel services are under review.
There is also disruption to some city services in Cork where diversions are in place.
Some flights at Dublin Airport are still being delayed because of the bad weather.
Delays of between 30-40 minutes and a few hours are being experienced.
Passengers are advised to contact their airline in advance of travelling.
There are no major delays at Cork, Shannon or Knock.
Trains running as normal
All Iarnród Éireann services are now running to schedule.
Overnight weather conditions
A widespread hard frost is expected tonight.
Temperatures are expected to fall between 0 and -7C and could go as low as -10C in sheltered areas.