Met Éireann has issued a severe weather warning of sleet or snow over the northern half of Leinster, Ulster and north Connaught as well as higher ground in Dublin and Wicklow.
Several flights in and out of Ireland have been cancelled, with forecast blizzard conditions threatening to wreak widespread travel disruption.
Motorists have been warned to take extreme care amid hazardous conditions as snowfall of up to 10cm is predicted in some parts of the country. Parts of Wicklow and Meath were impassable, the AA cautioned.
With gale force winds, rain, sleet and hail expected over the weekend, Irish Rail said it was monitoring parts of its network which are at risk from flooding.
Blizzard conditions are expected in some parts of the country throughout the day.
Aer Lingus was forced to cancel at least 16 flights between Ireland and the UK, as heavy snowfall across the Irish Sea hit airports in London, Bristol, Cardiff and Bournemouth. Ryanair has also axed a number of services.
Flights from Dublin, Cork and Belfast are all affected - with destinations of Heathrow and Britstol also seeing disruptions.
Air passengers planning to travel over the coming days have been urged to check their flight is going ahead before leaving home.
"Southeast to east winds will reach gale force this afternoon, evening and for a time tonight on Irish coastal waters from Rossan Pt to Carlingford Lough to Carnsore Pt and for the Irish Sea," said the warning from Met Éireann.
"West to northwest winds, later becoming north to northwest will reach force 6 or 7 this afternoon and evening on coasts from Mizen Head to Slyne Head to Rossan Pt."
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