"It's moving over the lower North Island, so we're just seeing progressively colder air moving up over the South Island and lower North Island,'' Mr Noble told APNZ.
Residents of Wellington's hill suburbs reported snow falling but not settling on the ground, with snowfall not expected lower than 300m above sea level.
Police said hail, rain and patchy snow was falling on the Rimutaka Hill between the Hutt Valley and Wairarapa, where the temperature had dropped below 1C.
The New Zealand Transport Agency (NZTA) warned 10cm or more of snow was expected this evening, with a significant chance the Rimutaka Hill would be closed overnight.
Police have urged motorists who have to travel over the hill to do so sooner rather than later, and to drive to the conditions.
Snow was also expected on the Desert Road stretch of State Highway 1 in the central North Island.
The snow is forecast about the central North Island ranges from Taihape and the Kaweka Ranges of the Hawkes Bay to northern Manawatu.
Heavier snow showers were starting to ease in the lower South Island, but parts of Canterbury would still receive some fairly intense showers, especially around Bank's Peninsula and the upper South Island.
That would be followed by a gradual easing in all areas tomorrow.
"So by the end of tomorrow most of the showers and snow should clear away those freezing levels should be starting to rise, so it's very much an improving trend as we go into tomorrow.''
Dunedin this morning awoke to a bitterly cold spring morning with strong winds and snow falling in the hill suburbs.
Dunedin resident Sally Boult tweeted this morning that it is snowing heavily at Blackhead Road and starting to settle while other Twitter users have posted photos of the snow.
Southlanders awoke to assess the damage after a night of strong winds gusting up to 120km/h.
Winton dairy farmer Donald Kidd said the bad weather had come as a bit of a surprise.
"This is the worst we've had for nearly two months actually. We've had a very, very mild spring - almost a bit of a shock actually. A reminder of how wintry Southland can be.''
He said the wind ripped around all night, and was continuing this morning.
"I'm surprised some power lines didn't come down somewhere because it was very strong and very cold, very cold winds. We're getting a bit of snow now a bit of a sprinkling of snow on the ground at the moment.''
Federated Farmers mid-Canterbury dairy spokesman Hamish Davidson said while conditions were far from ideal, they were prepared for it.
"Most dairy farmers are a fair way through calving now so snow or anything like that hopefully won't hang around too long and we'll have enough feed on hand.'' The conditions were more concerning for newborn lambs.
Some Southland roads remain closed by snow, including SH94 between Te Anau and Milford Sound, while the NZTA has warned motorists to use chains on some other roads.
The cold snap was welcomed by southern skifields, with yesterday's snowfall following up to 1m over the weekend, resurrecting a ski season that might have ended early.
Snow fell intermittently at Cardrona, the Snow Farm and Treble Cone skifields yesterday, with more expected today before conditions cleared tomorrow.
More on how roads have been affected can be found here.
- Additional reporting Otago Daily Times
