The Desert Road was closed overnight as icy conditions forecast through to Sunday morning.
The road had to be closed earlier today and several cars stranded there needed the help of a snow plough and a tow truck to get out.
Metservice says a strong, cold southwesterly flow over the country would gradually ease today.
There is still the possibility for severe southwest gales at Banks Peninsula, Kaikoura, Wairarapa, Hawke's Bay and Gisborne especially along the coast.
A previous threat of heavy snow for Stewart Island and southern Fiordland has now passed.
A severe weather warning for heavy snow in Otago and Southland had been in place on Saturday but MetService said most of the snow was expected to have stopped falling overnight Saturday.
Meteorologist Sarah Haddon said there was a gradual easing trend over the next day or so.
"There's still showers affecting Southland and Otago areas, and some of those will be sleety, with snow falling as well. But in the next 24 hours or so, that's an easing trend and tomorrow should be a relatively clear, fine day for most in the South Island."
Ms Haddon said there were still heavy showers in Waikato and off the Waiarapa Coast, and snow was falling in higher areas.
Temperatures were expected to plummet overnight and be even colder Sunday night through to Monday morning.
'It's bitterly cold'
Athol farmer Robert Durling was at a cafe when he saw a vehicle spin off the road and went to its aid.
There had been about 12cm of snow in the hills and about 8cm on State Highway 6, he said.
"It's bitterly cold and there's a good south-easterly blowing which I would call 'biting' - that would be an understatement.
"The roads are very slick with slushy snow... The roads are quite treacherous."
The Transport Agency said State Highway 87 between Sutton and Outram, State Highway 85 between Kyeburn and Omakau, and parts of State Highway 1 between Waitati and Dunedin were closed because of snow.
Flights in and out of Queenstown Airport were cancelled or delayed earlier on Saturday because of snow on the runway.
People living in Dunedin reported wet snow settling as low as 100 metres above sea level, with up to 15 centimetres forecast to accumulate above 400 metres.
Snow was also falling at Dunedin Airport but flights were not affected.
Metservice meterologist Tom Adams said it was the first big snowfall of the year.
"The bulk of the snow has been in the lowe South Island. Areas above 400m have seen some quite good accumulations - in Kingston I saw a recording of 12cm there.
"There have been numerous other places recording several centimetres - in Ranfurly, in Clinton, which is as low as 200m."
The cold front was moving up the North Island with more rain expected in Auckland later this afternoon, Mr Adams said.
While it would remain cold, most of the country should see blue skies tomorrow, he said.
South-west gales are also due to sweep southern and central New Zealand.
Yesterday MetService forecaster Chris Brandolino said the strongest west to south-westerly winds, of up to 110 km/h, would hit more exposed areas of the eastern South Island.
But the wind could also get "pretty strong" in parts of Taranaki and Waikato.
The Interislander ferry has stopped taking bookings for Sunday, when swells are predicted to reach six to seven metres.
A good inch here in Cromwell.❄❄❄❄☃ pic.twitter.com/2eVauRH7AE— Malcolm Rees-Francis (@Pno_nwa) May 19, 2017