Snow is falling in parts of the South Island as a bitterly cold front sweeps up the country.

Twizel and Fairlie saw some snow on Wednesday morning and there are falls on State Highway 8, Aoraki Mt Cook Highway and the Crown Range Rd, while Arthurs Pass was closed due to snow on the road.

MetService meteorologist Tuporo Marsters says Invercargill got the first wave of about four fronts from about 3pm on Tuesday.

He says it will get colder every time a front goes through, and by the time the last one hits, temperatures will be icy, with the very last front bringing snow to sea level.

'Don't put your woollies away ... even in the North Island.”

A few areas could hit October records, either for the coldest overnight temperature, or coldest daily high​ over the second half of this week, says MetService meteorologist Angus Hines.

A heavy snow watch is in place for parts of Otago, Canterbury and Marlborough from late Tuesday, including for Christchurch and Banks Peninsula from 1am Wednesday to 3pm Thursday.

A watch is also in force for Wairarapa including the Tararua Range south of Mt Bruce, and the eastern hills of Wellington. Road snowfall warnings were also in place.

Cantabrians will wake up to a rainy, chilly day on Wednesday, with snow down to 200 or 300m, but a gap in the weather would bring some reprieve in the afternoon, Hines says.

But later on Wednesday 'there will be even colder temperatures arriving, bringing another drop in temperature, more wet weather, and this time it is forecast to bring snow level right down towards sea level”.

Snowfall is expected to continue throughout Wednesday night and into the early hours of Thursday morning.

'It's quite a nasty wintry start to the day on Thursday, showers and snow flurries early on.”

It is 'pretty severe” weather for October, Hines says.

'It's unusual to see the risk of snow to sea level this time of year, particularly around Christchurch, but even further south.”

By Thursday evening, the weather is forecast to improve, slowly warming up for a weekend of sun and temperatures back in the mid-teens, Hines says.

Niwa has warned the cold snap could bring hypothermic risk to people and livestock, but being forewarned is key, Federated Farmer Otago president Mark Patterson says.

Farmers are 'well-prepared” for snowfall and cold temperatures, Federated Farmer Otago president Mark Patterson says. Photo: Peter Meecham/Stuff.

Farmers have had 'good warning”, so will be able to get stock to shelter.

'Fortunately most of the lambing is through on the lower country, it's just high country guys getting into it now.

'They'll be well-prepared for that sort of thing, it's not unprecedented.”

Pegasus Bay Winery marketing manager Ed Donaldson says it's 'a bit nerve-racking, but we have to deal with it every year”.

Frosts always have the potential to damage new shoots, budding between September and November, but Pegasus has a few ways to minimise losses, including wind machines, frost pots and sprinklers, Donaldson said.

Waka Kotahi journey manager Tresca Forrester warns 'short road closures” may disrupt school holiday travel, but snow is not expected to settle on most highways.

Chains needed to be carried from 5pm on Tuesday at the Homer Tunnel, State Highway 94, and cold sleety weather elsewhere could make driving conditions hazardous, she says.

'Slow down, allow extra time, turn on your lights and watch following distances.

'If you are travelling across the island please pack warm clothes and food, in case of disruptions on the road.”

-Carly Gooch/Stuff.