The North Island's Desert Rd is now closed, snow flurries are falling across central Christchurch and air travel is disrupted in the south as a fierce polar blast moves up New Zealand, bringing icy conditions, rain, and high winds.
Despite a few hours of reprieve from the snowstorm in the South Island yesterday, a cold front hit Stewart Island about midnight, and was expected to bring freezing levels down as low as 100m, the MetService said.
Those low freezing levels will work their way up the country today.
Metservice meteorologist Tom Adams said the main centres of Invercargill, Dunedin and Christchurch had largely escaped the snow, although hill suburbs in the latter two cities could expect light falls.
Snow was forecast to fall around 100m above sea level in all three places, and there was sleet at Dunedin Airport early this morning.
"It's trying it's hardest to snow ... and there could be more sleety showers."
in Christchurch, emergency services' staff reported snow flurries this morning. But the white stuff was likely to stick mostly to the hills, Adams said.
"Will it snow on the beach? I doubt it. Will it snow in the hills? Quite likely."
Invercargill Z petrol station worker Tawhiri McPherson said no snow had fallen in the city, but he understood one of their stations in Balclutha may have to close today because of snowfalls.
A significant amount of snow is expected to fall across the Central Plateau, Hawke's Bay ranges and Wellington region as the cold air invades the island.
Police say a truck and trailer unit rolled just after 1.30am near Waihohonu Bridge on the Desert Rd, blocking the main highway between Rangipo and Waiouru.
It was expected to take several hours to clear.
No one was injured in the crash and diversions are in place around National Park.
Extensive warnings went out yesterday as much of the country was set to freeze.
A number of roads are closed by snow across the South Island including SH1 north of Dunedin between Waitati to Pine Hill. Key major alpine highways including Arthurs and Lewis Passes are closed. Many others are affected by ice.
Last night 10 passengers were rescued from a bus that flipped near Makarora, between Wanaka and the West Coast.
At least one flight has been cancelled out of Dunedin this morning because of snow.
A Fire and Emergency spokesman said snow flurries had been falling on central Christchurch from 3am.
Those in the Wellington region may wake up today to find snow on the Rimutaka Hill Rd, but the real thing to watch out for will be the high winds around the south coast of the North Island.
MetService meteorologist Ravi Kandula said areas around Wairarapa and Wellington could be looking at wind gusts up to 100km/h and a mean wind speed of 50 or 60km/h.
All ferries across Wellington Harbour were cancelled today.
Offshore, winds could reach "storm-force", though it wasn't expected to be quite so ferocious on land.
"Basically, the south coast is not a place to be," Kandula said.
Those winds would "start to really ramp up" in the afternoon and evening.
Shortly after 1pm yesterday snow began falling, though not yet settling, in the Queenstown Lakes District, and the council warned chains must be fitted for anyone driving on the roads.
Civil Defence authorities were telling people to prepare for bone-chilling conditions as the wild weather headed north.
The Queenstown Lakes District Council said there were two crashes - one on State Highway 6A near Yewlett Cres involving a truck rolling, and another on State Highway 6 near Boyd Rd.
The council said temperatures were well below freezing and ice was forming on all roads, especially through shaded areas and over bridges. Freezing fog in many places was adding to hazards.
WeatherWatch's forecast team said behind the front, most places were dropping to mid to low single-digit temperatures - but things were not as cold as they could have been.
"Remember while this is a bitterly cold wintry event with severe weather potential, it's not an Antarctic storm so the air being dredged up is not as cold as it could be."
Niwa was labelling yesterday's weather as the "worst storm of the year'' for Otago.
Niwa climate scientist Nava Fedaeff said snow was expected to fall across the province for three days.
Yesterday was expected to be the heaviest day of snowfall, with up to 25cm in some parts, and the most exposed region would be East Otago, she said.
Snow was expected to fall in Dunedin and would settle on the hills, but snow falling at sea level "would not stick'', Fedaeff said.
It would bring with it hazardous driving conditions.
"Be careful on the roads. It has been cold and icy the last few days and now there is snow in the mix.''
The storm would be the worst of the year, but she doubted it would break records.
"July is the heart of winter when you get your big storms and freezing temperatures. So far, it has been cold, icy and fog has caused disruptions [in Otago] but it's not in the record books.''
The weather also disrupted travel across the country. Flights were cancelled and ferry sailings halted because of 7m predicted swells in the Cook Strait.
Numerous road closures around the South Island also caused a headache for motorists.
Potentially damaging gales are also expected to whip through North Canterbury, Marlborough and Nelson until Thursday.
When and where the worst weather will strike
Snow falling below 500m
Southland and Fiordland: Until Wednesday afternoon.
Otago: Overnight, until Wednesday evening.
Canterbury and Marlborough: Until Thursday afternoon.
Snow below 1000m
Taihape and Hawke's Bay ranges: From this afternoon until Thursday morning.
Northern Canterbury, Marlborough, Nelson, Wellington and Horowhenua Kapiti Coast: From this afternoon until overnight Thursday.
Wellington and Coastal Marlborough: During Thursday.
Wairarapa: From Thursday morning until Friday morning.
How cold will it be?