A Status Yellow snow-ice warning is in effect for the country, with gardaí advising motorists to take "extreme caution" because of poor driving conditions in many parts of the country due to snow.
Met Éireann has issued an updated warning, saying that further falls of sleet and snow are expected this evening. The forecaster said there would be further accumulations leading to slippery roads.
Gardaí have said driving conditions are poor in the midlands on the M4, M7, and M8. Met Éireann said conditions would clear early tonight, but would turn icy overnight.
The warning is valid until 8am tomorrow morning.
Motorists are advised to avoid harsh breaking, acceleration or steering, and are urged to drive with care in a high gear with their lights and wipers on.
The AA has said that most areas are returning to normal but there are still serious issues on the M7.
It says there is a tailback northbound at Kildare and that some motorists are reporting journey times of between two and three hours.
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Motorists were earlier urged to avoid parts of the M7 and M8 motorways in Laois and Kilkenny as sections of both motorways were closed due to extremely poor driving conditions.
It has said that Kildare, Tipperary and Laois are among the worst areas affected by snow.
In Kilkenny, the M8 between junctions three and four were closed due to four collisions on the north and southbound carraigeways.
In Laois, the M7 had also closed at the toll plaza past junction 18 following an incident.
The AA says snow and ice are also causing problems on local roads in Cork, Kerry and on the Sally Gap in Co Wicklow, which has now been closed.
Driving conditions are most difficult in Kildare, Tipperary, Kilkenny, Offaly, Laois, Meath and Westmeath.
The weather has caused a number of delays and cancellations at Dublin Airport with some passengers complaining of waiting on the airfield for over three hours.
A spokesperson for Dublin Airport said the runway and airfield remain operational but some aircraft have to be de-iced and this is causing knock-on delays.
Aer Lingus announced that a total of 12 of its flights in and out of Dublin airport were cancelled because of poor weather conditions there and gale force winds in Britain.
Dublin airport's website shows that airlines had not shown a status update for most of the 76 planes scheduled to depart from mid afternoon until 9pm.
A total of 21 were shown to have taken off while there was no status update for 37 Ryanair flights.
There were complaints on Twitter from passengers complaining that they had been "on the tarmac" for over three hours while another complained that a plane was still waiting for a gate to disembark an hour after landing.
Many of the arrivals were shown to be coming in two hours after their scheduled time.
Met Éireann says snow would have cleared into the Irish Sea by now but that as temperatures drop and snow and slush freeze, driving conditions will be challenging.
Joanna Donnelly of Met Éireann said motorists can expect tricky conditions overnight as any remaining snow freezes.
"There are a few accumulations here and there on lower levels which will turn into slush, and thats going to freeze overnight tonight as the skies clear," she said.
She added: "You can expect some tricky travelling conditions through this evening and overnight tonight and tomorrow morning too until this all clears through".