Motorists are being urged to drive to the conditions as snow and ice settles on roads after the cold snap.
The lower South Island was blanketed in snow on Tuesday, forcing the closure of schools and disruption at airports. In the North Island, major stretches of highways, including the Desert Road and Rimutaka Hill Road were closed.
The weather improved on Wednesday but drivers are being warned to take care.
The Milford Road on State Highway 94 in Fiordland reopened on Wednesday but motorists are advised to use chains.
The New Zealand Transport Agency advises extreme care also is needed on State Highway 85 between Palmerston and Kyeburn, and State Highway 87 between Outram and Middlemarch, due to icy conditions.
In the North Island, the Desert Road on State Highway 1 has reopened on Wednesday after being closed overnight.
The Rimutaka Hill Road connecting Wairarapa and Wellington is also open again, but light snow showers are expected to continue above 300 metres for most of the day. Extreme caution is advised.