Motorists have been urged to exercise extreme care on the roads as many New Zealanders wake to the heaviest frost of the year.
Temperatures plumetted overnight, causing "severe" frosts in parts of Otago.
Alexandra reported a hard frost with temperatures between -4degC and -6degC, and advised caution on bridge decks, hill sections and shaded areas.
There were severe frosts in the Queenstown area too. Glenorchy Rd was wet and icy in places from the Fernhill Roundabout out to Bobs Cove, the Queenstown Lakes District Council reported.
SH6 was icy through the Kawarau Gorge and you'll encounter ice and grit between Arrowtown and Queenstown via Arthur's Point, on the Crown Range and Cardrona Valley Roads, Wanaka, Hawea, Hawea Flat and Mt Aspiring Road.
The New Zealand Transport Agency warned there is fog on State Highway 8 between Twizel and Omarama.
The North Island is being hit by the cold snap too, with temperatures in parts of Waikato also dropping as low as -4C. Auckland got away lightly but still shivered through sub-zero lows as cold as -2C in some suburbs.
There are also heavy frosts around Rotorua and Taranaki, which are both down to -3C, about 7.30am.
Even Northland is down to -2C, with widespread frosts in sheltered inland areas.
Kaitaia in the Far North was on just 1C at 7.20am.
WeatherWatch analyst Phil Duncan said it was the coldest morning so far for many places this year, with frosts stretching from Southland to Northland.
He said more heavy frosts could be expected tonight, especially in the North Island, as the centre of the high currently over the South Island slid northwards.
"But frosts may not be quite so heavy in some southern areas due to more cloud and a breeze developing overnight in some areas," he said.
