An icy blast is set to engulf the whole of New Zealand after snow hit some South Island roads this morning, making Arthur's Pass off limits for a time.
More snow is expected overnight as a wintry blast hits across the country.
MetService has a heavy snow watch in force overnight from 6pm tonight for Fiordland and inland parts of Southland, Clutha and Otago.
Snow levels are expected to drop as low as 200 metres in the lower South Island.
Showers with heavy thundery falls and hail are expected for western and southern parts of the country.
Snow levels are forecast to drop to 700 metres in the Central Plateau with heavy showers expected for western and central areas of the North Island.
Tomorrow, MetService forecasts more cold wintry showers with possible thunderstorms in some coastal regions, and snow levels lowering to 100 metres in the deep south of the country during the morning.
The forecaster says temperatures are set to plummet for all the main centres, with Auckland and Northland getting down to four to six degrees with strong gusting winds, while the capital is expecting gale force southerlies and showers.
"We'll be seeing this system slide through. It'll actually be bringing its risk of snow tomorrow during the day across parts of the North Island. So the Rimutaka could be seeing some snow there through the afternoon, Desert Road as well," said Dan Corbett, 1 NEWS meteorologist.
Mark Owen of the New Zealand Transport Agency says the Central North Island is in for freezing conditions tonight.
"We've heard predictions of minus four in Waiouru. So that will make for challenging driving on State Highway One on the Desert Road, and if we feel its unsafe we will close it," he said.