Met Éireann has issued a status yellow weather alert, warning of heavy rain and strong winds in parts of the west and northwest.
Heavy rain is forecast from 9am on Christmas Eve to 9am on Christmas Day in counties Donegal, Leitrim, Mayo and Sligo. Local spot flooding is also expected.
A wind warning for Donegal, Galway, Mayo and Sligo will take effect from midnight on Christmas Eve until 8pm.
Met Éireann has also issued a weather warning for Christmas Day in Munster and Leinster.
It said that rain is likely to become persistent and heavy throughout the day.