Road conditions are expected to remain icy for most of the day in some areas, with temperatures barely rising above freezing.
Met Éireann said that Mullingar recorded the lowest overnight temperature at -6.5C.
However, forecaster Joanna Donnelly said it would gradually start to get milder.
She said last night was the last extremely cold night, but that it would probably dip below feezing tonight too for a time, at least in the east.
"It's slowly going to become milder from the west as temperatures start to rise," she said.