Motorists are advised to take care on the roads around the country due to snowfalls as a result of Storm Fionn.
Four weather warnings are in place as temperatures drop and snow and sleet sweeps across many parts of the country.
A Status Orange wind warning for Donegal, Galway, Leitrim, Mayo, Sligo, Clare, Cork and Kerry is in place until 3am as Storm Fionn will bring wind speeds of 65 to 80 km/h and gusts of up to 120 km/hr.
A Status Yellow snow and ice warning for the entire country remains in place until 9am on Wednesday morning.
Snow showers will move across Ulster and Connacht before reaching most other areas throughout the day.
Met Éireann has also issued an alert for very high seas along the Atlantic seaboard over the next few days, which may lead to coastal flooding.
It will be very cold today with wintry showers and strong winds and temperatures will drop to -1C overnight.
Around 2,000 homes, farms and businesses in counties Cavan and Monaghan are without power and supply is unlikely to be restored until Wednesday evening.
The Road Safety Authority and AA Roadwatch have urged motorists to take care on the roads, particularly drivers of high-sided vehicles during the strong winds.
Co Monaghan is among the worst-affected areas, with extreme caution advised on the N2 Dublin/Monaghan road, while part of the R188 Monaghan/Cootehill is impassable.
The Sally Gap in Co Wicklow is also impassable due to snow, while all routes around Roundwood village are very snowy.
A full list of affected routes is available here.
Snow is falling in Ballybay Co Monaghan as a weather warning for snow and ice is in place for many parts of the country pic.twitter.com/v2r5P8n74Q— RTÉ News (@rtenews) January 16, 2018
Snow and sleet showers have brought disruption to parts of Northern Ireland.
The Met Office has issued an amber weather warning with several inches of snow expected this evening and overnight.
Police have advised motorists to take extra care due to treacherous road conditions in some areas.
A number of schools in rural areas closed early because of the wintry conditions.
Galway City Council plans to close a section of Salthill Promenade during high tide this evening and tomorrow morning, as a precaution against possible flooding.
The road between Seapoint and Grattan Park will be closed to traffic ahead of this evening's high tide just after 5pm.
Some water is expected to breach coastal defenses along the promenade, with strong winds forecasted.
The overall risk of a repeat of widespread flooding, like that seen in the city earlier this month, is thought to be slight but homes and businesses have been advised to be vigilant to the threat, should conditions deteriorate.
There have been a mix of hail showers and blustery conditions in Galway this afternoon.