A status orange warning for rain in parts of the south east has been extended until midday.
Met Éireann says additional accumulations can be expected in Waterford, Wexford and Wicklow, with flooding in places.
A yellow alert for Carlow, Kildare, Kilkenny and Cork has also been extended until midday.
Accumulations of rain overnight have led to hazardous driving conditions.
The Road Safety Authority has issued a warning for motorists.
“Drivers need to slow down and leave a bigger space between themselves and the vehicle in front in wet weather conditions,” it said in a statement. “This is especially important on high speed roads such as dual carriageways and motorways where there is increased danger of aquaplaning.
“Flooded roads that appear shallow could be deeper than you think. They may also have trees or branches that have fallen that may not be visible."