In a rare event, almost the entire South Island has woken up to temperatures below zero degrees today.
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MetService meteorologist Stephen Glassy said the coldest place in the South Island overnight was Pukaki aerodrome near Twizel which reached a bone chilling - 19.8°C.
One of the few exceptions was Banks Peninsula, which made it to 1°C.
Mount Cook got to - 12.5°C, Invercargill reached - 4°C, Queenstown - 7°C, Dunedin - 5°C and Christchurch got to - 3°C.
In the North Island, Taupo got to - 3°C and Auckland airport measured just 3°C.
The all time record low is - 25.6°C recorded in Ranfurly in 1903.
The ice that caused major disruptions on South Island roads this morning, is not expected to ease for some hours.
Transport Agency manager Lee Wright said the severity of the black ice caught many drivers out, resulting in several crashes around Christchurch in particular.
Mr Wright said the driving conditions were very challenging and drivers should allow more time for trips.
A section of road between Christchurch and Akaroa has reopened after being closed for several hours this morning because of a fatal crash.
One person died in the crash in the Gebbies Valley area, and another was taken to hospital in a serious condition.
Further south, the Transport Agency said there was black ice on State Highway 90 from Raes Junction to McNab and State Highway 87 from Kyeburn to Outram.
There is ice and snow on some other highways including State Highway 94 from Te Anau to Milford Sound and State Highway 8 at Lindis Pass, from Tarras to Omarama.
Power still out for many
Some people in the Canterbury region have been without power since heavy snow brought down lines last week.
Line workers have been working to restore power, using helicopters to get to isolated places.
A farmer at Kimbell near Farilie, Sue Kerr, who has been without power since Thursday, said people were well-prepared for power outages, with coal ranges and wood burners, generators and gas cookers.
But she said the freezing temperatures were more of an issue, with about 20 centimetres of snow still covering the ground.
"I did hear of one story this morning where the lady was driving the vehicle to take the children to the school bus and the diesel waxed in the vehicle on the way, it was that cold.
"The stock side of things, that sort of starts to become a problem when the water starts freezing and they haven't got water to drink. You can feed them baleage and barley but they do need actual running water to be able to drink. We've got 2500 sheep and a couple of hundred cattle, they're standing around on snow... they just wait for us to come and feed them every day."