Freezing rain, snow and ice are just some of the hazards Met Éireann has warned of over coming days.
The national weather forecaster, its counterpart in Northern Ireland and local authorities have warned of very cold conditions featuring freezing fog, frost and ice with at times, rain, sleet, lying snow and dangerous driving conditions.
The Road Safety Authority has also added its voice to the warnings, advising those planning to drive or walk to consider if their journey is really necessary.
Met Éireann said an earlier status yellow warning for “localised danger” in counties in the northwest has now been extended for all counties overnight on Wednesday, until midday on Thursday.
Met Éireann also extended its general weather advisory for cold conditions to continue until 9am on Friday. It said sharp to severe frosts and icy stretches on roads and footpaths could be expected along with showers of hail, sleet and snow with the potential for freezing fog.
[ Storm-battered California gets more wind, rain and snow ]
In Northern Ireland the UK Met Office issued a status yellow warning for snow and ice across the six counties with wintry showers bringing further disruption.
A number of schools in Co Donegal were disrupted on Tuesday due to snowfall on roads, as well as some schools in Co Cork.
Met Éireann Forecaster Brandon Creagh said lying snow was likely to remain on the ground in the northwest. Wednesday night would be “very cold with frost and icy stretches” developing in many areas, leading to hazardous conditions.
He said a feature of the cold snap would likely be “freezing rain” which he said was “super cold rain falling on a freezing cold surface and turning to ice immediately.” Freezing rain has severe implications for motorists and other road users.
Thursday morning should see outbreaks of rain and sleet in the West and south with isolated wintry showers elsewhere. As the day goes on however, it will become mostly dry and bright, although some patches of mist and fog may linger as winds stay light and variable.
It will be cold with highest temperatures of 1 to 5 degrees.
While it is expected to remain cold with occasional wintry showers, temperatures are expected to increase by the weekend.
Mr Creagh said Thursday night should see temperatures dip as low as minus 4 again although it will be dry, becoming cloudy overnight with rain or sleet developing across Connacht, Munster and parts of south Leinster.
Patches of mist and fog are likely, in light and variable winds.
On Friday slightly warmer conditions are expected to set in with highest temperatures of 3 to 8 degrees, coldest in Ulster and Connacht, with a light southerly or variable wind.
On Saturday the warmer conditions will continue to spread from the south patches of rain and drizzle and temperatures rising to highs of between 7 to 11 degrees, in a moderate southerly breeze.
Saturday night should be much milder than recent nights, with minimum temperatures of 7 to 9 degrees, in a light to moderate southerly wind. Cloudy with rain in most areas, heaviest in the West and southwest.
Sunday is expected to be another mostly cloudy day with scattered outbreaks of rain. Highest temperatures of 9 to 12 degrees with light southerly winds. The outlook is for conditions to stay mild and quite cloudy for the early part of next week, with rain at times.