A status orange low temperature/ice warning has been issued for 19 counties, including Longford, Roscommon and Leitrim.
It will apply from 6pm tomorrow until 12 noon on Thursday.
Met Éireann says there are indications milder conditions will return at the weekend.
A national status yellow low temperature/ice warning remains in place until Friday for the whole country.
Met Éireann's Joanna Donnelly says there are a few difficult days ahead:
Not so much tonight, tonight we're only going as far as minus 5
But tomorrow night, we're going below that so there's an orange warning out for that
It looks at the moment that Thursday night will be much colder too.
So Wednesday and Thursday mornings will be very tricky mornings.