Met Éireann has issued a status Orange alert with air temperatures set to fall as low as -5 or -6 degrees tonight in Munster and Leinster.
It will be dry for much of the coming night with clear skies for most areas. But the north and northwest will become cloudier throughout the night and some light rain or sleet will develop in coastal districts later.
Lowest temperatures will be -2 to -6 degrees, giving sharp to severe ground frost widely but turning less cold in the north and northwest later.
An Orange level weather warnings is for weather conditions capable of having a significant impact on people in the affected areas. It implies that those in the affected areas should prepare themselves in an appropriate way for the anticipated conditions.
Prevailing winds tonight will be mostly light, north to northwest.
Earlier in the day a Yellow weather warning had been in place; at 8 am it was -2 degrees but it transpired to be a sunny and dry day for the most part.
Highest values during the day touched 6 degrees.
Roads are set to deteriorate later in the evening as temperatures slip below zero and motorists are advised to proceed with caution.