Blizzard-like conditions have been seen across Christchurch and the Port Hills, with several roads now closed.
The Christchurch City Council said deteriorating weather had forced it to close the Akaroa Summit Road from Little Akaloa to Okains Bay, Okains Bay Rd from Duvauchelle to Okains Bay and Little Akaloa Rd.
A long list of Banks Peninsula roads were restricted to four-wheel-drive vehicles with chains. These are:
- Akaroa Summit Road from Okains Bay to Le Bons Bay
- Le Bons Bay Rd
- Akaroa Summit Road - Le Bons Bay to Long Bay Rd/Cabstand
- Long Bay Rd from Takamatua to Goughs Rd
- Akaroa Inner Harbour - minor hill and rural roads
- Northern and eastern bays roads - minor hill rural roads
- Kinloch Rd/Bossu Rd
- Southern bays roads - Magnet Bay to Lands End Rd
- Little River to Gebbies Pass - minor rural roads
- SH75/Hilltop road, Cooptown to Barrys Bay
- Purau to Port Levy road
- Akaroa Summit Road, Hilltop to Pigeon Bay
- Pigeon Bay Rd, Duvauchelle to Pigeon Bay
- Akaroa Summit Rd - Pigeon Bay to Little Akaloa
The council said snow was continuing to fall in the area, with motorists advised to take extreme care.
Snow ploughs and other snow-clearing equipment was on the road.
Meanwhile, secondary school runners in the annual cross-country championships at the Halswell Quarry endured driving sleet and bitter winds.
Miserable conditions were also suffered by those at the annual Christ's College-Christchurch Boys' High School rugby match at Rugby Park.
However, Christchurch Hospital and St John reported no incidents relating to today's cold weather in Christchurch.
St John spokesman Ian Henderson said the ambulance service's workload had been steady, but there had not been any reports of cold-related incidents in the city.
However, St John had had "some minor issues" getting to patients further down the South Island. "In some instances we've had to use rescue helicopters."
St John encouraged people to stay warm inside and keep an eye on elderly friends, family and neighbours, he said.
"The cold weather is set to continue a little while yet, so people want to make sure they are as prepared as they can be."
Mt Hutt staff were busy today after 15 centimetres of snow fell last night.
Snowmaking has been running at maximum flow, with temperatures sitting around -8 degrees Celsius.
Little Akaloa Bay resident Grant Waghorn said he could see "just white" from his window.
He said a "big squall came through", dumping "a couple of inches" of snow.
It was not at sea level yet, he said, but was settling about 100 metres up.
Waghorn had been travelling home from Lyttelton when the snow hit at about Little River, he said.
"If I had left 15 minutes later I probably wouldn't have been able to get back," he said.
The snow was falling at intervals and had largely stopped now, he said.
Helen Patterson, of Whakamoa Bay, said she had snow about an hour ago, but was now getting "sleety, hail showers through".
The snow was not settling, but temperatures were hovering around 2.7C.
"I think we're getting off quite lightly," she said.
Christchurch residents have reported lunchtime snow flurries acros the Port Hills and as far out as Taylors Mistake.
Snow fell heavily further south overnight, though Canterbury initially escaped the brunt of the polar blast.
MetService forecaster Liz Walsh said temperatures plummeted to just 2C at Christchurch Airport about 6am today.
A gale warning has been issued for the coast south of Christchurch to Moeraki, and the swell could reach 4 metres.
The coastline north of Christchurch has been issued with a storm warning, with violent seas and 4m swells.
Snow fell mainly on Banks Peninsula and areas around the Southern Alps, Walsh said.
"The rain came late last night and because of that the freezing level lowered and we got snow," she said.
Cooptown recieved 11.3 millimetres of "a mixture of sleet and snow" overnight and Le Bons Bay received 8.6mm. Snowfall had stopped by 4am.
The Canterbury Plains, in particular near Mt Cook, also got "quite a dusting", Walsh said.
Parts of the Hurunui District got 4 centimetres, but Porters Pass, which initially had a snowfall warning, got ony 6mm of snow overnight.
Sleet and showers would continue throughout the day in Canterbury to near sea level.
"We are expecting there to be sleety showers about the coast today. Further inland it will be dry and very cold," Walsh said.
"It's not going to be exactly pleasant conditions. There will also be some late snow showers scattered through the Canterbury Plains."
However, Canterbury was missing the wintry blast Otago and Southland would continue to be battered by today.
Snow was creating havoc for passengers at Dunedin, Queenstown and Invercargill airports.
Air New Zealand flights NZ5949 and NZ5012 from Dunedin to Christchurch were both delayed about an hour.
Flights NZ5374 from Queenstown to Christchurch and NZ5080 from Queenstown to Christchurch had been cancelled.
Flight NZ8056 from Invercargill to Christchurch had also been cancelled.
The cold front was expected to have moved off the cost of New Zealand by tomorrow, with temperatures rising to a high of 13C and steadily rising throughout the week.
NZ Transport Agency spokesman Pete Connors said the only highway affected was State Highway 73 through Arthur's Pass.
Chains were essential through the pass and it was closed to towing vehicles, he said.
"We had snow in other parts of the network, like Lewis Pass and Amberley, but we had several snow ploughs out working there to clear the roads," he said.
"The message we'd like to get across here is that temperatures have dropped significantly and people should just allow a bit more time on their journey."
South Islanders battle polar blast
Snow is causing problems for drivers on many South Island roads as bitterly cold southwesterly winds cover the country.
Just before 6am, the Dunedin City Council warned of widespread snow and treacherous conditions in its area, and advised motorists to be extremely cautious.
Snow caused the cancellation of all Dunedin City bus services early today, while many schools in the city and surrounding area were closed for the day or opening late.
MetService said continuous snow showers had fallen overnight around southern parts of the country.
"They're going to get these snow showers continuing throughout the day," forecaster Elke Louw said.
Some light snow showers were expected in the Queenstown area.
Snow closed SH8 between Roxburgh and Alexandra, while SH94 between Te Anau and Milford Sound was also closed because of falling trees and heavy snow.
SH1 between Dunedin and Waitati was closed to towing vehicles by snow.
Chains were needed on some other South Island highways.
MetService data showed the temperature dropped to -1C in Alexandra early today and is not expected to climb above 3C today.
Dunedin's expected maximum is 6c, while Christchurch is expected to get to 4C, Wellington to 8C and Auckland to 13C.
- The Press