Temperatures could drop as low as minus three tonight.
Met Éireann's cold weather advisory is to remain in place until Saturday morning.
It's warning of widespread frost and ice, as well as hazardous travelling conditions.
Alan O'Reilly from Carlow Weather says the current cold spell is here to stay:
"It'll become a little bit less cold for the next couple of days. Temperatures will you get up to 5°C or 6°C during the day, but still frost at night. It's good high pressure. It's nice and dry so it will be mainly dry now. Small chance for a few showers on Friday but they will be rain if they came, put then around Monday or Tuesday next week, there's a high risk of much colder air coming back".
