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MetService meteorologist Lewis Ferris said overnight temperatures - particularly tomorrow and Wednesday - would be lower than they have been so far this year.
He said high pressure and cold southwesterlies would cause overnight temperatures to drop drastically, with frosts in the morning.
"It's a classic set-up for winter. We've had these southwesterlies over the country which have brought the temperature down. With it being winter now it's not unusual to get widespread frost for parts of the country."
Frost was the main concern, he said.
"It's going to be just a cold winter's night, so make sure you've got the wood stocked up and an extra blanket on the bed. But in the morning be careful with frosts around and take extra care on the roads."
Sheltered inland parts of the South Island and central North Island were likely to experience frosts and icy roads.
MetService is advising people to stay updated with the latest forecasts and its Severe Weather Watch for heavy snow and strong winds which remain in force for parts of southern New Zealand.