MetService said "freezing conditions" descended across much of the South Island, bringing a sub-zero start for some places and very low single-digit temperatures elsewhere.
There were heavy falls of snow in inland Otago, which closed sections of State Highway 87 and SH85 for most of the morning. In an update at 12.30pm NZ Transport Agency Waka Kotahi advised both highways had reopened, but urged motorists to take care.
Snow also fell in some Dunedin hill areas, including on the higher reaches of the city's Northern Motorway (SH1).
A traffic management truck rolled at the top of the motorway, partially blocking the road for a time. Police said the accident occurred about 7.10am. No-one was injured and the vehicle had to be towed. They weren't aware of any other issues on the roads.
Other places, including Alexandra and Timaru, got down to 1C, while Dunedin, Oamaru and Queenstown dropped to about 2C.
"Tonight, however, will be a colder night for many spots with places like Te Anau and Alexandra set to drop to -3C and even Christchurch set to drop down to -1C," MetService meteorologist John Law told RNZ.
"The cold air will be making its way northwards and even parts of the lower North Island will drop down cold enough for a touch of frost."
In an update at 8.10am, the council said roads had been cleared and snow had stopped falling in the area. However, caution was advised around Moa Flat and the Beaumont hills due to snow.
The CODC said the Danseys Pass Road was closed from the gates passed the Danseys Pass Hotel.
An Otago Daily Times photographer at the scene said some trucks had lost traction on a stretch of the Pigroot (SH85), bringing traffic to a halt for a time, shortly before the road was closed.
The Queenstown Lakes District Council advised that there was snow on the Crown Range Road and chains were required by motorists heading that way.
The Milford Road (SH94) was closed for a time reopened about 9am and was expected to remain open throughout the day.
- Allied Media/additional reporting RNZ
