Met Éireann has said that tonight will be extremely cold with temperatures plummeting to between -1 and -7C.
A Status Yellow low temperature and ice warning is in effect until midday tomorrow.
Hazardous icy conditions are expected in places with a widespread severe frost and pockets of freezing fog.
But conditions are forecast to improve in the west and northwest from early tomorrow morning.
Due to the widespread icy conditions, AA Roadwatch says particular care is needed on secondary and minor roads.
Motorists are advised to slow down, leave extra space to brake, and keep manoeuvres gentle while driving.
The very cold northerly airmass over us, with tonight being the coldest night of the season so far, will be replaced next week by a much milder Atlantic airstream bringing more unsettled weather with it. pic.twitter.com/BzjfIWhlwT— Met Éireann (@MetEireann) January 8, 2021