Road users have been warned to exercise extreme caution when driving today with Met Eireann predicting overnight snowfall.
Moderate to high accumulations of snow were expected, with Ulster, Connacht and much of Leinster and north Munster said to be the areas most at risk.
Between 3 and 6cm of snow was predicted generally, but as much as 10cm was due to fall in some parts, particularly in parts of the north midlands and Ulster.
The snow was expected to spread across the country throughout the night, with temperatures estimated to drop to minus 2 or 3 in some midland areas.
Some heavy rainfall was also predicted for much of south Munster and the far south of Leinster, with any snow affecting mainly mountains and high ground.
The overnight snow combined with frost is expected to make driving conditions extremely difficult.
The Road Safety Authority, AA Roadwatch and the Garda have all urged drivers to exercise caution and to avoid any unnecessary journeys.
Motorists are advised to check local and national weather forecasts before setting out on a journey and to remember that it takes longer to stop in icy conditions than on a dry road.
They are also advised to avoid harsh braking and acceleration, to use dipped headlights and to reduce speed in heavy snowfalls.
AA Roadwatch advised that the most treacherous road conditions will be on back roads and on high ground.
The cold snap was already having an effect yesterday evening in Wicklow, where the Sallygap to Roundwood Road was blocked by snow and motorists had to take alternative routes.
"Bad weather such as ice and snow can catch road users off guard," said Noel Brett, chief executive of the RSA yesterday. "Therefore in such weather conditions it is best to avoid making any unnecessary journeys. If driving in such conditions is unavoidable, be prepared. The golden rule is drive with care and expect the unexpected."
Pedestrians, cyclists and motorcyclists are advised to wear bright clothing with reflective armbands or a reflective belt or to carry a torch.
Dublin City Council gritted roads as a precaution in the early hours of the morning, but were not expecting any major problems in the city.
A Met Éireann spokeswoman said that weather would remain quite cold over the next few days, with snow expected to turn to rain or sleet. Maximum temperatures today will be 1 to 8 degrees.