The status yellow alert kicks in from 7.00am
Met Éireann has issued a status yellow snow-ice warning for 20 counties.
The warning is in place for Connacht, Cavan, Monaghan, Donegal, Dublin, Kildare, Laois, Longford, Louth, Wicklow, Offaly, Westmeath, Meath, Kerry, Limerick and Tipperary.
The forecaster says there will be patchy accumulations of up to 3cms of snow for a time on Thursday and Thursday night.
It says this will be especially on higher ground, but small amounts will also be at lower levels.
The alert is in place for parts of Munster between 7.00am and 4.00pm
And it will come into force for parts of Leinster, Connacht and Ulster from 4.00pm onwards.
Met Éireann adds that rain will follow, clearing any snow.
The alert is in place from 7.00am on Thursday until 6.00am on Friday.