Met Éireann forecaster Gerry Murphy advised people to expect a “multi-hazard weather event” over the weekend and into next week.
He said there would be sleet and snow in many areas on Saturday evening and into Sunday.
“It will most likely fall as rain down the south coast but it must be said that the amounts of rain expected in the south and south-west are quite high, so it’s likely that we will see rainfall warnings, at least, in the south-west of the country,” Mr Murphy told RTE’s Radio One.
“Then, as that rain pushes up through the afternoon/evening, it turns more to sleet, as you go in the hours of darkness then turning more to snow – currently, it looks like – predominantly over the southern half of the country.
“Then over much of the Midlands, the west, perhaps tomorrow night early on.
“Counties in the north-east mightn’t fare too badly because there is an easterly wind.
“It’s very difficult to pinpoint but really as we go through tomorrow night into Sunday all areas can expect sleet or snow at some stage.”
Mr Murphy said it would not be clear until the weekend whether schools would open on Monday when they can see how much snow has accumulated.
“There are likely to be accumulations of snow in places on Monday morning coupled with a very severe frost as well.
“So there is the possibility that schools may not open but that will become more apparent as we go through the weekend.”
He said into next week, low temperatures will continue which will make it difficult for snow to melt.
A spokesperson for the Department of Education said in a statement to the PA news agency that it was monitoring weather developments.
“A decision on whether to remain closed or to delay school reopening times is a matter for individual school management authorities around the country in light of local weather conditions, taking into consideration the full guidance and direction available from the principal response agencies.
“Any decision to close is taken in the interest of child safety, having assessed the local risks and having consulted, as appropriate, relevant authorities.”
A Status Orange snow and ice warning has been issued by Met Éireann as Ireland is set to be hit by a "multi-weather hazard event" over the weekend, with significant snowfall expected.
The Orange warning will be in effect from 5pm Saturday until 5pm on Sunday for Carlow, Kilkenny, Laois, Offaly, Wicklow, Clare, Limerick and Tipperary.
What was originally a Status Yellow rain and snow warning for Cork and Kerry from 1pm on Saturday until 5pm on Sunday has also been upgraded to an Orange warning from 5pm on Saturday.
Met Éireann said it could lead to very difficult travelling conditions, travel disruption and delays to public transport (air, rail and bus), animal welfare issues and difficult conditions underfoot.
There is a risk of sleet or snow in all parts of Ireland this weekend which could see schools stay closed on Monday, forecasters have said.
Sub-zero temperatures are expected for the coming days, with people urged to take care on the roads during the cold snap.
Leinster, Connacht, Cavan, Donegal, Monaghan, Clare, Limerick, Tipperary and Waterford will all also be under a Status Yellow snow and ice warning from 5pm on Saturday until 5pm on Sunday.
Met Éireann forecaster Gerry Murphy said conditions had taken a “cold and sharp” turn and people should expect a “multi-hazard weather event” over the weekend and into next week.
He said there would be sleet and snow in many areas on Saturday evening and into Sunday.
“It will most likely fall as rain down the south coast but it must be said that the amounts of rain expected in the south and south-west are quite high, so it’s likely that we will see rainfall warnings, at least, in the south-west of the country,” Mr Murphy told RTÉ’s Radio One.
“Then, as that rain pushes up through the afternoon/evening, it turns more to sleet, as you go in the hours of darkness then turning more to snow – currently, it looks like – predominantly over the southern half of the country.
“Then over much of the Midlands, the west, perhaps tomorrow night early on.
“Counties in the north-east mightn’t fare too badly because there is an easterly wind.
“It’s very difficult to pinpoint but really as we go through tomorrow night into Sunday all areas can expect sleet or snow at some stage.”
Mr Murphy said it would not be clear until the weekend whether schools would open on Monday when they can see how much snow has accumulated.
“There are likely to be accumulations of snow in places on Monday morning coupled with a very severe frost as well.
“So there is the possibility that schools may not open but that will become more apparent as we go through the weekend.”
He said into next week, low temperatures will continue which will make it difficult for snow to melt.
The Dublin Region Homeless Executive has said 82 additional beds can be made available if required during the cold snap.
It said that it will monitor the situation over the coming days and activate the additional accommodation if a weather warning is announced.
The executive has asked people to notify them of people sleeping on the streets via its website or app Dublin City Rough Sleeper Alerts.
Alone has also urged older people to take particular care to avoid slipping on icy paths.
Slips, trips and falls in over 75s can have serious and even fatal consequences, with an average of 20 per cent of older people dying within a year of a hip fracture, it said.
The organisation asked people to look out for neighbours who may be challenged, or more isolated because of the cold snap.
