Met Eireann has issued a Status Yellow rain warning for counties Donegal, Galway and Mayo today.
People are being advised to expect spells of heavy rain at times with accumulations of 30 mm possible.
The alert was issued from 9pm Wednesday to 9pm Thursday.
Tonight will be windy with the rain clearing eastwards, followed by blustery scattered showers.
Friday will also have a risk of heavy and possibly thundery showers.