Road-safety chiefs have warned motorists, cyclists and pedestrians to take extra care in the hazardous conditions.
They also appealed to cyclists to wear high-vis jackets to ensure they are seen by motorists.
A quarter of all road fatalities this year have occurred on a Friday and yesterday the AA's Conor Faughnan said drivers needed to be careful on roads over the weekend.
"We are getting lots of minor collisions and accidents. Road conditions are poor, so please slow down." The Garda urged road users to reduce speeds, use dipped headlights and keep a safe distance from the vehicle in front.
The warning came as Met Eireann have forecast more torrential downpours and spot flooding with a risk of isolated thunderstorms.
Dublin, Meath, Wexford, Carlow and Kildare will bear the brunt of scattered showers and flash floods today and tomorrow – but the whole country can expect thundery downpours.
Met Eireann has issued a "level one" yellow weather warning, which gives a 5pc to 15pc chance of severe weather conditions and means 'be aware'.
Today will begin with hazy sunshine in the west and north of the country.
However, showers in the south and east will spread to most areas during the afternoon with up to 25mm of rain forecast.
It will continue to be mild, with temperatures of between 14C and 17C, warmest in the west.
Cork City Council have issued a flood alert until Sunday, with residents in areas including South Terrace, Trinity Bridge, Rutland Street, and Cotter Street especially at risk.
Dart and rail chiefs do not expect services to be affected by the conditions.
The outlook for early next week is bleak, with dank and dreary weather.