Icy roads are causing problems in parts of the South Island with vehicles losing control on ice in Dunedin and one hitting the side of a bridge.
Three Mile Hill Road in Dunedin was closed due to ice and Mount Cargill is closed due to snow.
There was ice on Stuart Street in the city and on bridges south of Dunedin on State Highway 1, while SH1 is closed from Waitati to Dunedin.
A dozen roads about Dunedin city are also closed with all council gritting trucks out working on the network.
Ice on the runway has delayed flights in and out of Dunedin airport until further notice.
Air New Zealand said four flights to and from Auckland and Christchurch were cancelled, and other services have been delayed.
Snow fell overnight in the Alpine passes in the South Island as well as the Desert Road in the central North Island.
Waka Kotahi Mark Owen told Morning Report snow and ice have closed two highways out of Dunedin, State Highway 87 from Outtram to Middlemarch and State Highway 1 north of Dunedin.
"For other roads that are open we just advise extreme caution, black ice is really hard to detect."
Black ice was typically caused when it rained and then it froze and was very hard to detect and dangerous to drive on, he said.
Snow is making some South Island travel difficult, closing State Highway 73 through Arthur's Pass, SH63 St Arnaud to Renwick, SH7 from Springs Junction to Hanmer Springs and SH6 from Kōhatu to Kawatiri Junction.
Owen said people should check before they travelled because other roads may be closed as the day progresses.
In the North Island, ice has closed the Desert Road and it could be closed for some time, Owen said.
The Remutaka Hill Road may also be affected depending on how far down the snow comes, he said.
Things could change rapidly depending on how the bad weather moved north but there will definitely be cold temperatures over the next 48 hours and motorists should drive with caution, he said.
MetService meterologist Andrew James said the last of the snow was starting to pull away from Marlborough but overnight snowfall affected the alpine passes.
Temperatures plummeted overnight, reaching -6C at Tekapo, and a combination of cold temperatures and wet roads has led to icy roads, he said.
That wet weather from the south was moving across the lower North Island making for a wet start to the day in Wellington.
Road snowfall warnings were in place for Napier-Taupō Road (SH5), the Desert Road (SH1), Remutaka Hill Road (SH2), Lewis Pass (SH7), Arthur's Pass (SH73), Porters Pass (SH73), the Crown Range Road and the Dunedin to Waitati Highway (SH1).
James said cold temperatures would last at least until the weekend. "The next couple of nights are going to be the coldest," he said.
