Met Éireann has issued a status yellow rainfall warning for several western countries.
The alert is in place for Galway, Clare, Kerry and Limerick for 24 hours from Friday afternoon.
The forecaster says spells of heavy rain will lead to accumulations of 30 to 40mm during the period.
While higher totals are possible in upland areas.
Overall, Friday will see overnight rain and fog clearing northwards in the morning.
There will be some dry, bright spells for a time - but more showery rain will push in from the Atlantic.
There will also be some heavy and possibly thundery bursts in places.
Top temperatures of 12 to 15°C.
Friday night will see heavy showers throughout with indications of high rainfall accumulations in the southwest.
There will also be strong winds around western and southern coastal regions.
Lowest temperatures of 3 to 5°C.