Conditions in the North Island were not forecast to be as bad as last Sunday when a snow storm closed State Highway 5 between Napier and Taupo, stranding hundreds of travellers.
However, conditions would be "very wet" and at higher altitudes "very snowy", Mr Duncan said.
Like last week the weather was caused by a cold southerly moving up the South Island, while a large low pressure system crosses the North, he said.
The MetService has issued road snowfall warnings for Arthurs Pass, Porters Pass, Lewis Pass in the South Island and the Desert Road and Rimutaka Hill Road in the North.
The last cold snap wiped out hundreds of newborn lambs and farmers are being advised to consider moving stock to lower levels or sheltered areas this weekend.
Police are urging motorists to drive to the conditions and be prepared.
The end of the school holidays would see many travelling long distances home, Canterbury traffic manager Inspector Al Stewart said.
" Check the weather and road conditions before you leave so you can change your plans and route if necessary."
People should also check their vehicles had good tyres and a full tank.
"There are many roads and passes in our district which are quite remote and susceptible to snow and ice.
"There are often quite long distances between refuelling stations and places to get advice."
Mr Stewart urged divers to slow down when necessary, keep windows clear, not overtake in risky situations an d pull over to let faster vehicles past.
Drivers should get plenty of sleep and take regular breaks to combat fatigue, he said.
"Eat sensibly and ensure you remain hydrated, but avoid large meals as they can make you drowsy."
- NZPA
