About a hundred motorists have been brought down safely from the Rimutaka Ranges, near Wellington.
The motorists became trapped after snow forced the closure of the road at about 6pm, police said.
As the polar blast sweeps north, snow was reported in Palmerston North, Feilding, Dannevirke, Waipukurau, Hawera and Stratford.
Drivers are being warned to stay off the roads from Canterbury to the lower North Island as snow, ice and flooding causes treacherous conditions.
In Wellington some are abandoning their cars, as heavy rain and snow blankets Wellington down to sea level.
Wellington Emergency Management Office is warning against unnecessary travel during the rough weather, which has brought with it the heaviest snow seen in the capital in decades. Thousands were without power this afternoon in northern suburbs.
Wellington Electicity spokesman Drew Douglas said everyone in Wellington, Upper Hutt and Plimmerton had their power reconnected by 9pm. He said as far as he knew, no-one else was without power in the region.
Icy conditions have caused localised flooding and made roads dangerous, and emergency services are assisting motorists in the worst hit areas.
Police inspector Mike Coleman said reports of drivers running into trouble were coming in from many of the city's higher suburbs including Wanuiomata Hill, Churton Park, and Karori.
At least one car had gone through a fence and police were attending breakdown callouts when they could.
"There'll likely be more problems in the morning with people taking kids to school and that sort of thing."
No incidents of injury or serious accidents had been reported.
Wellington Electricity said 2800 customers were without power in Tawa since a power cut at 5.20pm.
All but 380 customers, mainly in Grenada, were reconnected by 5.50pm.
Snow has fallen from Karori to Pukerua Bay, blanketing cars, houses and roads.
Broadmeadows resident Mark Stevens said cars were sliding backwards down the slopes of the northern suburb of Khandallah.
He was forced to leave his car at the bottom of the hill and walk 30 minutes home with his daughter.
"I had to stop because cars were sliding back into me," he said.
"Cars were eschewed on the road, sliding around or not moving."
What began as a snow flurry just before 5pm soon settled to make for dangerous driving conditions.
Within half an hour emergency services were on the roads and cars were being abandoned, Stevens said.
However, children unaccustomed to snow in Wellington were seen throwing snowballs and riding down the slopes on boogie boards.
The snow fall was similar to what Stevens saw when he lived in Central Otago.
"It's absolutely surreal."
Temperature plummeted to just below 3 degrees Celsius in Wellington today.
Kelburn resident Peter Kemp said it was the largest snow fall he had experienced in Wellington.
Like many residents, he was cranking up the heater and taking shelter indoors.
Wellington City Council spokesman Richard MacLean said after several calls from the public about high water levels and water being flooded onto neighbouring properties by traffic, a decision had been made to close the road. It will reopen when water levels subside.
Rongotai Rd in Kilbirnie has been closed due to heavy rain.
Snow fall has also been reported widely across the South Island.
Canterbury police were urging motorist to take care and if possible avoid driving.
"We are asking the public to stay at home and delay all non-essential travel if they do not think they can travel safely in their local conditions," Inspector Al Stewart, Canterbury Road Policing Managers said.
Dunedin Police Senior Sergeant Mel Aitken said snow was falling intermittently all morning.
WeatherWatch.co.nz analyst Richard Green said the whiteout conditions might not occur for some however the next wave is still likely to be more widespread and heavier.
Motorists are being warned to take care on the Desert Rd where snow showers are likely to dump up to 15cm of snow today and up to 30cm on Monday.
The Rimutaka Hill road could also become treacherous as snow starts to fall from about 3pm to midnight. Up to 8cm is expected to pile up tonight.
Heavier falls will develop tomorrow morning with up to 30cm expected.
Interislander ferries are still crossing the Cook Strait. Waves of up to 2m have been reported.
Once waves reach 5.5 passenger ferries would be cancelled. Freight ferries can continue until waves reach roughly 6.5m, an Interislander spokeswoman said.
Mt Ruapehu ski fields had 5cm of fresh snow in the past 24 hours. Turoa now has a 218cm base and Whakapapa has 167cm. Both are open but not all lifts are functioning.
The MetService last night warned people to stay at home rather than venture out as a cold front moved up the country, bringing air direct from Antarctica.
"Strong southerlies, gale about exposed coasts with the cold temperatures will make the wind feel bitterly cold and create blizzard-like conditions in some places," its forecast said.
At the other extreme, blossoms could be seen on Auckland trees.
However, strong winds and rain threatened to dislodge these first signs of spring.
MetService forecaster Geoff Sanders said the cold front was quite a significant event.
"It's a very cold outbreak and the strength of the wind associated with it will make it very cold. It leads on to Monday, where we could be looking at blizzard conditions in some inland areas - particularly the Canterbury high country."
An "extremely cold southerly outbreak" will see "significant accumulations" of snow in Fiordland south of Te Anau, Southland and Otago.
WeatherWatch.co.nz was predicting winds were going to be strong over the North Island tomorrow and on Tuesday.
Hundreds of Cantabrians queued for firewood yesterday. One operator said well over 1500 people had been through the gates since they opened at 7.30am, loading their cars and trailers with firewood.
"It's pretty crazy," City Firewood staff member Tineke Ward said. "We've loaded trailer after trailer. Cars have been backed up 200 metres down the road and having to wait about an hour."