Met Eireann has issued a status yellow warning for Cork and Kerry as heavy rain gets set to hit.
The caution follows a fresh wind alert for Donegal, Galway and Mayo, which are expected to see as gusts of 100km/h overnight.
The latest alert says that up to 40mm of rain will fall in the two counties, with local flooding possible.
It was issued at 7pm on Saturday, and is in place from 9am on Sunday for the entire day.
Meanwhile, the wind warning came into force at 11pm on Saturday, and remains active until 6am on Sunday.
And more poor weather is expected on Sunday even after Storm Aiden passes.
Met Eireann is expecting horrid conditions to hammer coastal areas all day with a status red marine gale warning in place.
The forecaster said: "Blustery on Sunday with some bright or sunny spells to start.
"However, outbreaks of rain will spread from the southwest through the morning and afternoon, becoming heavy at times and bringing the risk of flooding.
"Southwest winds will remain fresh to strong across southern counties, easing light to moderate elsewhere. Some patches of mist too. Highest temperatures of 10 to 16 degrees, coolest in the north and mildest in the south."
