A STATUS Yellow rainfall warning has been issued for Mayo.
It is valid from 9 p.m. this evening until 12 noon tomorrow.
Met Eireann is forecasting very heavy rain developing overnight and into Saturday with spot flooding, 25 to 35mm expected.
The rain may turn to snow in parts for a time.
Also covered by the warning are all Connaught counties, Longford, Offaly, Westmeath, Cavan, Monaghan, Clare, Cork, Kerry, Limerick and Tipperary.
St. Patrick's Day looks set to be a cold and blustery day with sunny spells and passing showers, some with hail and thunder.
Highest temperatures of 7 to 9 degrees in fresh and gusty west to northwest winds.
Showers will retreat to Atlantic coastal areas on Sunday night with good clear spells developing elsewhere. Lowest temperatures of 1 to 4 degrees.