It says a break in the weather will mean uncertain conditions
The Road Safety Authority (RSA) is advising all road users to exercise caution, following a forecast for heavy rain and possible thundery downpours this weekend.
It says the expected rainfall will bring to an end to the dry spell, which poses dangers to road users.
According to Met Éireann, scattered heavy rain showers will become widespread in Connaught, Cork, Clare, Kerry and Limerick from Friday evening and Donegal, Leinster, Cavan and Monaghan on Saturday.
RSA CEO Moyagh Murdock says: "Roads are at their most slippery when the weather breaks after a dry spell.
"When the weather breaks, this deposit mixes with rainwater and the road becomes hazardous.
"The resulting greasy road surface increases stopping distances and the risk of a skid. The sudden change in driving conditions can also catch drivers off guard."
"The expected rainfall and the condition of roads will make driving particularly hazardous as road surfaces become slippery reducing skid resistance", she said.
Drivers are being advised to slow down, drive at an appropriate speed to the conditions and not to tailgate - allowing extra distance to the vehicle in front.
It is also advising drivers to use dipped headlights at times of poor visibility, and check tyres to ensure minimum tread depth of 1.6mm and ensure correct tyre pressures.
It comes amid a new 'Operation Slowdown' campaign from the gardaí.
The operation started at 7.00am Friday morning and will continue until 7.00am Saturday morning.
Some 34,000 vehicles have been checked, with 106 travelling in excess of the applicable speed limit.
Some notable occurrences were: