Cars slid off roads in the south this morning after calm weather and clear skies cause temperatures to plunge overnight.
"The winds died out overnight and we had clear skies for much of the country which resulted in the drop in temperatures," MetService meteorologist Stephen Glassey said.
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With frosts in many places across the country, ice could be a concern, particularly in places where snow on the ground had melted and then frozen.
A late frost in Dunedin caused a number of vehicle crashes throughout the city.
State Highway 1 north of the city was closed after five crashes due to icy conditions at the motorways summit, Pigeon Flat, about 10 minutes out of the city.
The highway has now re-opened, Senior sergeant Craig Brown said.
Brown said one person was taken to hospital, however he was unsure of the nature of their injury.
Police attended about 15 other crashes around the city, with motorists caught out by a late frost, he said.
That included two cars that rolled, one in Portobello Rd, the other in Brighton Rd.
"The ice is definitely causing us some grief," Brown said, saying people were not driving to the conditions or watching following distances.
The ice became particularly slippery once it had sun on it, he said.
Police were urging motorists, particularly those in the hill suburbs not to venture out in their vehicles unless it was necessary.
Two vehicles had gone off the road in separate incidents in Southland on the Wallacetown-Lorneville Highway and a crash had been reported in Gore.
Around 6.30am MetService was reporting a temperature of -4.9 degrees Celsius in Queenstown.
Glassey said the temperature got down to -7C at Molesworth Station, -6C at Pukaki Aerodrome, Waiouru and Mt Cook, -5C on the Desert Road through the central North Island, and -4C in Christchurch. At Dunedin Airport the temperature dropped to zero.
In Auckland, the temperature dropped to 0.5C at Ardmore and 1C at Pukekohe. In Wellington, the temperature in Upper Hutt dropped to -2C but Kelburn was a warmer 4C.
Palmerston North Airport woke to a chilly -2.5 degrees.
"It's probably the coldest morning we've had so far this year but it's not uncommon as we head into winter, when we get these cold air masses come over and the winds drop off," Glassey said.
Despite the cold start, temperatures did not get as low as forecasters had thought they might.
Lindsay Bain from Trailview Lodge just outside Alexandra in Central Otago, told Radio NZ the temperature at the lodge dropped to -4C, well short of the -10 to -13C that had been suggested as possible.
MetService communications meteorologist John Law said despite that "it's a very cold start to the day".
"What we're looking at there is perhaps not the right conditions. The winds a little bit stronger, just encouraging a little more mix in."
About 300 Powerco customers in Tararua and Wairarapa were still without power this morning. The company expected power to be restored to all but the most severely damaged parts of the network by the end of today.
Overall, 6200 Powerco customers lost power since Friday evening due to high winds that caused trees to come down across powerlines.
"Reports from the field indicate around 90 per cent of the damage has been caused by trees breaking and falling into powerlines and many of the power cuts could have been avoided if the trees had been trimmed or felled to avoid problems," Powerco acting network operations manager Dean Stevenson said.
The NZ Transport Agency (NZTA) was urging caution on many highways, mostly in the South Island, as snow remained on the roads and ice formed. The only highways still closed because of snow this morning was State Highway 87 from Outram to Middlemarch. SH6 from Haast to Makarora was closed by rock falls.
In the North Island, NZTA warned of the need for caution on SH2 over the Rimutaka Hill between Wellington and Wairarapa.
Today's calm conditions will be shortlived, with heavy rain spreading into Fiordland and Westland tomorrow and winds rising to gale force in the centre of the country and the east of the South Island, MetService said.
A brief period of snow showers was likely in the south and east of the South Island as a cold southerly change moved in on Thursday.
In Dunedin the route of one bus service was altered because of icy road conditions and another service was delayed due to ice on the road. Primary and intermediate schools between Mosgiel and Port Chalmers and Waikouaiti were due to start at 10am.