The national forecaster has predicted a dramatic plunge in temperatures from Friday on, with daytime lows of just 4-5C likely over the festive weekend.
According to Met Eireann, a polar low event is to blame for the dramatic shift in temperature.
The thermometer will sink to -2 or -3 tonight, causing widespread frost formation and wintry showers on high ground.
The cold spell will last well into the weekend, marring the festive spirit perhaps.