Temperatures sunk to -3 to -5 degrees in the Midlands.
Drivers are being urged to be very careful on the roads this morning, after temperatures dropped to minus-five in parts overnight.
A status yellow low temperature warning is in place for all of Connacht, along with counties Cavan, Monaghan, Donegal, Longford and Cavan.
The alert runs until 10 o'clock this morning, but Met Eireann is warning of icy conditions for much of the day.
Rhode's Cathal Nolan, from Ireland's Weather Channel, says it will stay cold for the day: