A status yellow low temperature and ice warning will be in place from 6 o'clock in Leinster and Connacht.
Met Eireann is forecasting temperatures to dip as low as minus four in places.
The alert will run until 11am tomorrow morning.
Liz Gavin, forecaster with Met Éireann, says there is also a change of ground frost.
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"Our weather will be turning colder tonight than recent nights and we are going to see a widespread frost
"So temperatures tonight will fall between zero and -4°C."