"It is probably their coldest night this year," Mr Finnie said.
Temperatures at Dunedin Airport plummeted to -7C."It's out on the Taieri Plains so they get harder frosts out there than in the city, but even the city's down to 1C in the central city and some of the valleys in Dunedin will be a lot colder than that."
Christchurch, Hamilton and Taupo also reached sub-zero temperatures, he said.However, the chilly start to the day would lead to a bright day for most places.
"I don't think people will be too cut up about having a frosty morning."