Big freeze follows blast of Storm Clodagh
Overnight temperatures are to plummet as low as -4C in parts this week, as Arctic air from the North Pole sweeps across the country.
Strong winds and snow are also forecast, while a band of sleet, heavy rain, and icy gusts gather pace.
Reports of snow falling on some hills in Donegal were already circulating early this morning.
Much of the country is still reeling from the fallout of Storm Clodagh, which left 4,000 people without power and caused the cancellation of a number of flights.
Clodagh, the third named storm of the extended winter season, passed eastwards to the north of Ireland yesterday morning. It will push on through Scotland and the North Sea towards southern Scandinavia, where it is expected to deepen further. More than 45,000 people were left without power when 'Storm Barney' hit Ireland less than a fortnight ago.
Today will again start off windy along the south and west coasts, particularly in counties Waterford, Cork, Kerry and Clare. A series of heavy downpours will affect all parts for a time, and motorists are warned to watch out for spot flooding in places.
Met Eireann said sleet and hill snow will fall over Ulster, but as the day progresses conditions will turn drier and brighter in the afternoon, except for southern counties.
Temperatures will hit a high of 13C, but it will remain cold over Ulster at only 5 or 6C.
Tomorrow there will be extreme winds in southern counties, particularly in exposed areas.
Heavy rain in the morning will slowly clear northwards during the morning and early afternoon. However, damp, misty conditions, will continue to persist around Mayo, Clare and Galway, on exposed southern coastal counties, and close to higher ground.
The day will become windy, but also much milder with temperatures rising to around 13C in strong southwesterly winds. It will be mild overnight with occasional mist and drizzle.
There'll be more heavy rain on Wednesday which will spread from the west during the day, and further rain will move in during the evening.
Temperatures will be up to 13C but will tumble overnight, with lows of 0C and frost and icy stretches likely.
The east and south will be wet for much of Thursday, with the rain possibly turning wintry on higher ground.
But it will gradually brighten up across Ulster and Connacht, with temperatures hitting a high of 7C. Overnight will be clear and cold, with temperatures of -4C to 1C.
Met Eireann warned that with temperatures barely getting above freezing, there is a greater risk from icy conditions, particularly for motorists.
Drivers have been urged to drive carefully and within agreed speed limits.
They are advised to remember stopping distances can be up to 10 times longer in ice and snow.
Those brave enough to wrap up warm and venture outside on Friday will be rewarded with crisp weather, as chilly but dry conditions replace the sleet, wind and rain.