Met Éireann has issued a Status Orange snow and ice warning for counties in the west, midlands and east where significant falls of snow are forecast from tonight through the weekend.
Snowfalls of up to eight centimetres are forecast, with Met Éireann saying that temperatures could drop to as low as -6C.
The warning for this weekend covers Carlow, Kildare, Kilkenny, Laois, Longford, Wicklow, Offaly, Westmeath, Meath, Galway, Mayo, Roscommon and Tipperary.
Met Éireann has said that there could be "significant accumulations" of snow overnight and into tomorrow.
Met Éireann also warned of slippery paths and treacherous road conditions.
A Status Yellow warning is in place for counties Dublin, Louth, Wexford, Cavan, Monaghan, Leitrim, Sligo and Waterford.
Rain and sleet are due overnight and tomorrow with a risk of snowfall, especially away from coasts and on high ground.
Meteorologist Liz Walsh said: "Over the Dublin mountains and in the foothills of the Dublin mountains there could be some significant accumulations there but also there will be significant snow accumulations in parts of east Connacht, the north midlands and some snow occurring in parts of Munster and south Leinster."
"We are into a very cold night on Sunday night," she added.
The Met Office has also issued a yellow alert for snow and ice in Northern Ireland, with 2-5cm of snow forecast in many areas.
Snowfalls overnight across Northern Ireland brought icy road conditions this morning and appeals from the PSNI for motorists to drive with extreme care.
Due to the adverse weather, the speed limit on all motorways in the North was reduced to 80km/h.
Belfast Zoo was forced to close due to the conditions and some sporting fixtures have also been cancelled.
Motorists advised to drive with care on roads
The National Emergency Coordination Group met yesterday to discuss possible measures to deal with any potential issues arising from the severe snow and ice conditions.
It said that in addition to road salting, local authorities would be activating assessment teams to review conditions.
The group has said it is monitoring weather conditions.
Motorists have been urged to drive with care as snow and ice have been reported on many routes throughout the country.
Gardaí said: "Drivers should be aware that it takes longer to stop a vehicle on an icy road so slow down and allow extra distance between you and the vehicle in front."
Assistant Commissioner Michael Finn said: "Please be aware that visibility is reduced in snowy conditions so drive slowly if you need to make a journey. Allow extra distance between you and the vehicle in front. Motorcyclists/cyclists should not comprise their safety by their 'need' to travel in icy/snowy conditions. Be safe."
Minister for Housing Eoghan Murphy said arrangements are in place for rough sleepers as temperatures drop.
Minister Murphy tweeted that there would be safe shelter and food available "for everyone who needs it".
1/2 Contact with Dublin, Cork, Limerick & Galway has confirmed arrangements in place for rough sleepers. Teams already out in Dublin to help people in ahead of snow forecast for tonight and efforts will intensify in to the evening.
— Eoghan Murphy (@MurphyEoghan) December 9, 2017
2/2 There is safe shelter & food available for everyone who needs it. My thanks to our partners @PMVTrust who placed everyone they could get in last night (and still with extra capacity had it been needed).
— Eoghan Murphy (@MurphyEoghan) December 9, 2017
Dublin City Council said all of its gritting trucks will be out from 2am to salt 300km of key road networks.
Sligo County Council said the county's main routes will be treated but warned that conditions on local roads "are likely to be very difficult in the event of snow and ice".
