There is a nationwide warning for snow and freezing temperatures over the next 24 hours.
Met Éireann has issued a "status orange" warning for hail, sleet and snow in the west and north-west.
Up to 8cm of snow is likely on high ground in Connacht and west Ulster especially. Social media users in Donegal and nearby counties posted several photos of heavy snow early this morning.
Snowy Benbulben. pic.twitter.com/5ezAvZ3b1p— St.🍍 (@Spifeypineapple) January 13, 2015
— Joe duffy (@joeduffy888) January 13, 2015
Elsewhere a separate "yellow alert" is in place for Leinster, Cork, Tipperary and Waterford - with up to 4cm of snow expected in parts.
Joanna Donnelly from Met Éireann says the difference between land and sea temperatures is to blame, as the Atlantic Ocean is warmer than the land mass.
"The sea temperature is nine, ten, eleven degrees or so - [but] the land is very cold," she explained.
"We've got showers forming over the sea - they're going to die out as they get over the land, but initially they're going to be blown in … they're heavy, thundery, and it's so cold that they're going to fall as snow.
"The longer they go on, the more snow that's going to fall."
AA Roadwatch is advising caution in a number of areas including Sligo town, the N15 in Donegal and the Ring of Kerry where snow and ice are affecting driving conditions.
Age Action is warning that cold weather can and does kill in Ireland, as well as posing problems for the elderly community who could find it difficult to go out to buy groceries, fuel or medical supplies.
The charity's spokesman encouraged people to check in on elderly or vulnerable friends and neighbours.