25 to 50 millimeters of rainfall is expected, with the heaviest falls in mountainous areas.
The alert remains in place until 6am tomorrow morning.
A yellow alert is also in place in counties Limerick, Tipperary and Waterford.
A more serious orange warning applies for Cork.
Joanna Donnelly, meteorologist with Met Eireann says we’re in for a wet couple of days:
Meanwhile motorists are being advised to exercise extreme caution on roads around the county.
There are reports of heavy snow in many parts including the Killarney and Rathmore areas.
The Road from Killarney to Molls Gap is icy this morning and also there are icy patches on the main Killarney/Cork Road at the county bounds.