Met Éireann has issued a Status Yellow snow and ice warning for 18 counties nationwide.
All counties in Connacht are included, as well as Dublin, Carlow, Kildare, Laois, Longford, Louth, Wicklow, Offaly, Westmeath, Meath, Cavan, Monaghan and Donegal.
The warning will be in place between 6am and 6pm on Sunday.
The forecaster is warning of wintry falls of snow and the possibility of some accumulations.
Meanwhile, a national weather advisory for all of Ireland remains in place until midnight on Sunday.
Very unsettled weather is expected over the weekend, with wet and windy conditions bringing a risk of localised flooding.
It will also be cold across the two days, bringing wintry falls of snow and icy conditions.
Status Yellow - Snow/Ice warning for Connacht, Cavan, Monaghan, Donegal, Dublin, Carlow, Kildare, Laois, Longford, Louth, Wicklow, Offaly, Westmeath and Meath.
Wintry falls with some accumulations possible.
Valid: 06:00 Sunday to 18:00 Sunday 31/01/2021https://t.co/l8JdKfwZt9 pic.twitter.com/hygv4fb1rJ
— Met Éireann (@MetEireann) January 30, 2021
Temperatures will hit lows of -1 to 3 degrees Celsius tonight, with some frost and ice due to set in across more sheltered areas.
Rain will move into the west and southwest later in the night, followed by falls of sleet and snow, especially over Connacht.
Tomorrow will see wintry outbreaks of rain, sleet and snow become widespread in the morning.
It will be a very cold day generally with highest temperatures of 1 to 5 degrees Celsius.
Elsewhere, heavy snow, torrential rain and icy conditions are forecast to hit parts of the UK over the next few days.