Met Éireann has warned that temperatures could drop to -6C overnight and warned of a "treacherous start" to tomorrow morning with frost, ice and freezing fog patches.
It forecasts continued wintry showers in the north and west with some snow accumulations, sharp or severe frost and ice also.
A number of schools in Donegal will be closed tomorrow and in Northern Ireland a large number of schools have decided to close due to the weather conditions.
A Status Yellow Snow-Ice warning is in effect for Cavan, Donegal, Monaghan, Connacht and Louth and Met Éireann has said that other counties could receive some wintry showers.
The warning came into effect this morning and is valid until 11am tomorrow.
Temperatures are expected to fall to between -2C and -5C generally, with sharp or severe frost and icy stretches with black ice too.
Met Éireann is warning of hazardous travel conditions and poor visibility.
Meanwhile, a Status Yellow Low Temperature/Ice warning has been issued for Carlow, Dublin, Kildare, Kilkenny, Laois, Longford, Meath, Offaly, Westmeath, Wexford, Wicklow, and Munster.
That warning is valid until 11am tomorrow.
In Northern Ireland, the UK Met Office has issued a Yellow warning for snow and ice for Antrim, Armagh, Down, Fermanagh, Tyrone, Derry with the potential to cause disruption to travel into Monday morning.
The warning is valid until midday tomorrow.
Watch: Snow and icy conditions in Donegal as temperatures drop
Kerry County Council is advising all road users to travel with extra care tonight because of freezing temperatures and warnings from Met Éireann of the likelihood of icy conditions.
Kerry Council crews will be treating priority routes tonight in line with the Council's Winter Maintenance Plan.
All road users are being asked to travel with extreme care over the next few days, to allow extra time for journeys and to expect icy conditions as well as possible snow showers, particularly during the return to school commute on Monday morning.
