The wintry blast has hit the lower South Island, with snow closing the northern motorway out of Dunedin, several roads in Central Otago and sending a number of cars sliding off the road in icy conditions.
The bitterly cold blast, bringing snow down to coastal areas, is moving up the country today, bringing warnings for travellers and for farmers to get stock to shelter.
Queenstown Airport is closed this afternoon with all flights in and out either cancelled, diverted or delayed.
The New Zealand Transport Agency said Dunedin's northern motorway, State Highway 1, was closed around midday.
Towing restrictions and chains were essential for Porters Pass, SH93 Clinton to Mataura, SH6 Kingston to Dipton and SH94 between Milford and Mossburn.
Police asked motorists to slow down and the drive to the weather conditions in Central Otago and Southland.
Where possible, motorists are asked to stay off the roads.
The road from Lawrence to Milton, SH8, was closed and there is heavy ice on the Pig Route -- State Highway 85 from Ranfurly to Naseby.
Chains are essential in all vehicles and people should stay at home unless it was vital, said Sergeant Ian Kerrisk of Alexandra police.
There was severe ice and snow on SH6 south of Lumsden through to Kingston. A number of vehicles have left the road because they were travelling too fast for the conditions, said Senior Sergeant Dave Raynes of Invercargill police.
WeatherWatch.co.nz head analyst Philip Duncan said much of Southland and Otago was below or near zero degrees as the coldest air coming straight off the Antarctic ice shelf moved over the lower South Island.
There were reports of some light snow flurries in Christchurch and Dunedin, with "blizzard-like" conditions in Queenstown.
Mr Duncan said the coldest of the northbound air would eventually hit the mild, moist, conditions over the North Island and could create even heavier snow in the North Island and central parts of New Zealand.
"This isn't the snow storm of the century, many main centres won't have snow settling, but what makes this system different from previous cold blasts is the low snow level, which is sea level across much of southern and eastern South Island and to very low levels in the lower North Island," Mr Duncan said.
"It's not out of the question that brief snow flurries may fall in parts of Wellington and Taupo with a snow/rain mix overnight in Palmerston North and Masterton."
Mr Duncan says snow was very likely as far north as the Coromandel Peninsula. "I'd expect a dusting of snow on Monday across the Coromandel peaks and on Mt Te Aroha in the Eastern Waikato".
Snow could fall on the Hunua ranges south of Auckland on Monday, with sleet on the tops of the Waitakeres, Mr Duncan said.
The MetService has issued a heavy snow warning for southern Fiordland, Southland, eastern parts of Otago from Dunedin southwards, Canterbury from Christchurch and Banks Peninsula northwards, Kaikoura, the central North Island high country from Taupo to Taihape including inland Wanganui and Manawatu, Hawke's Bay and Gisborne.
A watch for heavy snow was in place for, Taranaki, Wairarapa, Marlborough, Nelson and remaining areas of Canterbury and Otago not covered by the warning.
Snow accumulations are likely to affect many roads and passes, these include most of those passing through the central North Island, the Napier to Taupo Road , the Gisborne to Opotiki Road, the Rimutaka Hill Road, the Lewis Pass, Arthur's Pass, Porters Pass, the Lindis Pass and The Milford Road.
Bitterly cold southerlies meant farmers were advised that stock may need shelter.