Snow is falling in Canterbury and several roads have been closed as a winter blast settles over much of Aotearoa.

A blast of cold air coming "straight from Antarctica" has brought snow fall in the South Island this morning as Wellington CBD will have its best chance of snow in a decade.

Shortly after 8am MetService issued a heavy snow warning for the far south of the South Island and Banks Peninsula.

"An intense cold outbreak spreads northwards over the country today and on Thursday, bringing unseasonably low snow to the South Island and the lower North Island.

"South to southwest gales are also possible, especially in the east from Invercargill to Wellington.

"Snow is likely to affect many parts of the South Island and lower North Island. Heavy snow watches remain in force for many areas and warnings have been issued for the far south of the South Island and Banks Peninsula. Note that significant disruptive snow is also likely to affect many other areas.

"People are advised to proceed with caution and keep up to date with the latest MetService forecasts and advice from the NZTA. This event will bring significant impacts to transport, livestock and crops."

The heavy snow warning for Southland, Stewart Island, Clutha, Dunedin, Central Otago south of Alexandra, the Southern Lakes District south of Queenstown, and Fiordland from Te Anau southwards is in place from 9am today to 9am tomorrow with 20cm to 30cm of snow above 200m.

The warning for Banks Peninsula is in place from 10pm tonight to 10am tomorrow and 10cm and 20cm is expected above 200m.

Traffic cameras captured early morning snow falling in Fairlie, in the Canterbury region, as snow arrived in the South Island.

Travel warnings

Caution is required on SH93 between Clinton to Mataura due to winter driving conditions. Further forecast snow may affect state highways and local roads throughout the South Island.

Please take extra care on all roads and plan ahead if you intend to travel on the network today/tonight.

CLOSED

• SH8 Tarras to Omarama (Lindis Pass) - Snow and Ice

OPEN CAUTION

• SH8 Cromwell to Tarras - Snow and Ice
• SH93 Clinton to Mataura - Snow

OPEN

• SH73 Arthurs Pass to Otira - Snow
• All other State Highways remain open

SH2 Kaitoke to Featherston (Remutaka Hill)

A strong winds warning is in place between Kaitoke and Featherston (Remutaka Hill), extra care is required especially for lighter or high-sided vehicles and motorcycles.

The snow has closed off State Highway 73, Arthurs Pass to Otirā.

NZ Transport Agency Waka Kotahi said: "Further forecast snow may affect state highways and local roads throughout the Canterbury and Otago regions."

Motorists are being warned to take extra care on the roads as a result and to plan ahead if intending to travel today or tomorrow.

Livestock in Glentunnel, a village in the Selwyn District, have already been dusted in snow. Metservice warned earlier in the week the unseasonably cold temperatures had potential to damage crops and stress animals.

Snow covered sheep in Glentunnel. Photo / George Heard

Severe weather watches

MetService has issued a number of heavy snow watches in several parts of the country.

People in Wairarapa, including the Tararua Range south of Mount Bruce, and the eastern hills of Wellington are advised of a heavy snow watch in place from 10pm to 4pm tomorrow.

"Snow may lower to near sea level during this time and amounts could approach warning criteria above 200m," the MetService said.

There is also a watch over Marlborough south of the Clarence River, the Canterbury high country and foothills, North Otago, Central Otago and Alexandra northwards - as well as the Lakes District from Queenstown northwards.

The heavy snow watch is in place until midnight tonight.

The weather authority is advising people in these areas that snowfall amounts could approach "warning criteria" above 400m.

The Canterbury coast and plains, including Christchurch and Banks Peninsula, has a heavy snow watch for the 38 hours that started at 1am today, until 3pm tomorrow.

Again, people are being told that snowfall amounts may reach warning criteria above 400m.

"Then from 6pm [today] to 3pm [tomorrow], snow showers may lower to near sea level and snowfall amounts could reach warning criteria to near sea level - especially about Banks Peninsula."

MetService advises that heavy snow watch might be upgraded to a warning.

Weather experts say the Wellington region is set to get large amounts of snow as a polar blast settles over the capital this evening and into tomorrow morning.

MetService meteorologist Jesse Owens said: "The worst of that [snow] will be in those eastern regions, so we'll expect larger amounts of snow to low levels."

The Tararua and Rimutaka Ranges will likely be covered, with around 5cm to 8cm of snowfall forecast for the summit of the Rimutakas.

However, Owens said snow could fall in the city centre for the first time since 2011.

"Anywhere in Wellington you could see snow. This is our best chance in a long while to see some snow. We're expecting down to 200 to 300 metres tonight and overnight tomorrow morning. It could get to sea levels."

Weather authorities have described the wintry blast as an intense, cold outbreak that will spread northwards over the country this week.

Snow is likely to affect many parts of the South Island and lower North Island, in particular, with temperatures set to drop and heavy snow watches in place.

Snow in October

Owens said the conditions were unusual for this time of year even though spring weather could be very changeable.

"We don't see it often and not in October. It's very rare and it is unusual to see an outbreak this cold this late in the year."

A crisp spring yet snowy morning in Maniototo. Photo / Supplied