Parts of Ireland will experience "freezing fog" as temperatures are set to plunge to -4C on Sunday night.
Met Eireann has issued a Status Yellow low-temperature warning for 22 counties as the mercury is expected to plummet.
The weather chiefs have warned of "widespread severe frost" ahead of what will be a "very cold" night.
A warning said: "Very cold tonight. Minimum air temperatures will range -2 to -4 degrees Celsius.
"Widespread severe frost with the risk of icy patches. Some pockets of freezing fog also."
The alert will be in place for Connacht, Cavan, Monaghan, Donegal, Carlow, Kildare, Kilkenny, Laois,Longford, Louth, Offaly, Westmeath, Meath, Clare, Cork, Kerry, Limerick and Tipperary.
The weather caution will be valid until 10am on Monday morning.
Motorists are being advised to take care on Monday as the bitterly cold weather is set to cause hazardous driving conditions.
The morning fog may be slow to clear, but a dry and bright day is to follow. Highest temperatures will range from 6C to 9C.
A forecaster said: "Very cold to start the day with frost and some freezing fog with hazardous driving conditions in places. The fog possibly slow to clear.
"A dry and bright afternoon will follow in most areas with good sunny spells.
"Highest temperatures generally 6 to 9 degrees but temperatures possibly a little lower where any fog lingers into the afternoon.
"Light variable winds will back southeasterly later in the day and freshen along Atlantic coasts."
