Temperatures are set to plunge to as low as -1C on Tuesday night - but it's not all bad news because three days of sun and warm conditions are to follow.
Tuesday will be a nice dry and mostly sunny day - hazy at times - with highs of 15C.
But it's going to get nippy overnight with temperatures expected to drop to below freezing point in some areas.
A Met Eireann forecaster said: "Cool and bright this morning, with any frost quickly clearing, then dry and mostly sunny for the rest of the day.
"The sunshine will be a little hazy at times, especially in the north with some high cloud. Winds light southeast or variable.
"Highs of 12 to 15 degrees, but a little cooler near south and southeast coasts due to the onshore breeze.
"A dry and cold night with long clear spells. Lowest temperatures of -1 to +2 degrees.
"Mist and fog patches will form in near calm conditions, fog becoming dense in parts of Connacht and Ulster."
However, it will get hotter over Wednesday, Thursday and Friday with highs of 16C or 17C on the way.
There will be long sunny spells across all three days, despite the odd shower on Thursday.
And a "stiffening easterly breeze" may take the edge of temperatures in Leinster on Friday.
Looking ahead to the weekend, Met Eireann said: "Cloudy over much of the country with patchy outbreaks of rain at times, particularly in the south and east.
"Holding mostly dry in the north and west with some hazy sunshine at times.
"Cooler than previous days with highs of 11 to 15 degrees, mildest in the west, in a moderate easterly breeze."
