Snow, sleet and hail are on the way as “bitterly cold” weather is forecast from Wednesday this week.
Several centimetres of snow are expected around the country as the cold blast is expected to last through the weekend.
Met Éireann forecasters said temperatures are expected to drop to minus 4 degrees during to the week.
A build-up of snow is expected , particularly in the north and west.
Wednesday is set to be a cold, blustery and showery day, with snow and sleet showers in the evening.
Severe frosts and icy roads are expected by night for the later part of the week.
Thursday and Friday will remain very cold with a wind chill. The highest temperatures will reach no more than 6 degrees.
It will continue to be very cold for the weekend as wintry showers continue.
Up to 10cm of snow, even in low level areas, has been forecast for some counties in Northern Ireland on Wednesday.
Met Office has issued a yellow alert for Co Antrim, Co Armagh, Co Down, Co Fermanagh, Co Derry and Co Tyrone.
It warned strong and gusty winds will come with snow showers leading to reduced visibility and “temporary blizzards” over high grounds.
Across the Atlantic, a massive blizzard has slammed into the US Northeast, and United Airlines cancelled its 9am Tuesday departure from Dublin to Newark.
Aer Lingus transatlantic flights to New York from Dublin (10.50am) and Boston (2pm) have also been cancelled, as has the 11am Delta Airlines flight to New York.
People flying with Aer Lingus can check for delays and cancellation on their website. Mountain rescue services were warning climbers to be very careful on steep ground following the rescue of three hikers from Carrauntoohil at the weekend.
Kerry team rescue spokesman Damien Courtney said conditions on the MacGillycuddy’s Reeks are very dangerous at the moment with hard packed snow in all gullies and ice exposed ridges.
Footage showed the rescuers climbing to near the top of Ireland's highest mountain to help the two men and woman who were stuck. None of the climbers were seriously injured.
