The Desert Rd in the central North Island has been closed due to heavy snow tonight and in parts of the South Island snow could reach sea level.
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Police communications Inspector Marty Parker said the Desert Rd stretch of State Highway One road was closed about 6.30pm. The road was not expected to re-open tonight.
MetService forecaster Philippa Murdoch said overnight heavy snow was also expected to fall to 200m in the southern South Island and up the western side of the Southern Alps.
In some areas flurries could reach sea level.
Most of the Central Plateau of the North Island - especially over 700m - will get a dumping of snow overnight.
Wellington would be dry overnight but north of the capital in Kapiti, and up to Taranaki, some thunder storms were possible tomorrow.
Eastern New Zealand from north of Dunedin to Hawke's Bay is mostly fine tomorrow with just a few showers expected in places.
Auckland and further north could expect some showers tonight and tomorrow.
Acting southern road policing manager Senior Sergeant Steve Larking said the chilly conditions and forecast showed that winter was "well and truly here".
He advised motorists to take extra care on roads around Southland and Otago as there had already been a number of crashes over the past week due to icy conditions.
"We remind people to get the latest information about road closures and the conditions of driving routes from NZTA [Transport Authority] or their local council and to plan their journeys according to the weather and road conditions."
The snow closed State Highway 94 from Te Anau to Milford Sound, while Porters and Lewis Passes, SH 80 from Pukaki to Mt Cook, and SH 8 from Fairlie to Twizel were closed to towing vehicles.
NZTA warned drivers to be cautious on SH 6 from Frankton to Kingston and on Lindis Pass.
Trucks were stranded in snow on SH6 near Glenhope, 83km south of Nelson, early this morning, but NZTA said the snow had since been cleared and the road was open.
Snow ploughs and gritting trucks were a common sight around Queenstown this morning, along with skiers and boarders flocking to the mountains to ride fresh powder after heavy overnight snow.
Snow was almost at lake level in central Queenstown and on the ground in Arrowtown.
The dumping closed the Crown Range road until 7.30am. With the Milford road closed indefinitely schools in the area have delayed opening until 10am.
Temperatures were as low as -7.5 degrees on the Remarkables skifield, which has received a 20cm dump, increasing its snow base to 50cm.
Meanwhile, Coronet Peak and Cardrona have received 30 cm and 25cm of overnight snow respectively.
Gusts of up to 150kmh were expected around Stewart Island today, and 120kmh gusts were forecast to spread over Wellington and the Wairarapa.
MetService warned that winds of that strength had the potential to damage trees, powerlines, unsecured structures and make driving hazardous.
In Stewart Island, roofs could be lifted. People were advised to be cautious and to stay up to date with the latest forecasts and warnings.