The Desert Road in the central North Island has re-opened late on Thursday morning after being closed for several hours, but motorists are being warned to take extreme care.
Snow, ice and high winds are also affecting many roads and highways in the South Island and conditions are expected to worsen throughout the day with heavier snowfalls expected.
In the South Island, wintry conditions are hitting many roads and alpine passes.
The Milford Road is closed, chains are essential on State Highway 73 over Arthur's Pass, while other highways, particularly in parts of Otago, are affected by snow, ice and high winds.
Motorists are advised to take care.