Few places will come through unscathed as a southerly storm rampages across the country bringing a cold, wet end to the school holidays.

MetService meteorologist Matthew Ford said the front was perched over Stewart Island early this morning, and would move up the South Island through the day bringing rain, dropping temperatures and even dumping snow to 200m in places.

The North Island's dream spring run would continue one day longer, with a northwest flow continuing to bring mostly fine, settled weather, and just the odd patch of cloud and occasional shower.

Temperatures would hover around the late teens in most places, with the east coast the pick of the bunch including Napier cracking 21C.

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Temperatures in the South Island would plummet as the icy southerly storm ripped through.

Dunedin would go from 19C yesterday, 14C this morning to 7C this afternoon and 6C tomorrow. Christchurch would see a similar drop in the mercury.

There was a heavy snow watch in force for inland parts of Canterbury and Otago, with potential snow down to 500m. In Fiordland and Southland it could fall to 200m.

Road snow warnings were in place for Haast Pass (State Highway 6), Lindis Pass (SH8), Crown Range Rd and Milford Rd (SH94) overnight, but these would likely be extended over the next few days.

The West Coast would see the most of the rain, however most places were in for a wet few days.

The front would arrive in the North Island from Thursday morning, spreading rain and cold southerly winds as it moved north.

"Thursday and Friday are not looking great," Ford said.

The front should track east across central and northern New Zealand, while a low was forecast to develop along the front and track east across central New Zealand on Friday.

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Ahead of the front and low, there could be heavy rain about Buller and Nelson ranges, and the Richmond Range on Thursday.

There was also a chance Mt Taranaki, the Whanganui headwaters, Tongariro National Park, and eastern Bay of Plenty could see some heavy rain later Thursday and into Friday.

Snow was forecast through this period to 400m about inland parts of northern Canterbury and Marlborough.

On Friday, the strong and cold south to southeasterly flow was expected to spread further across the North Island.

South to southeasterly gales could become severe in exposed parts of Wellington and coastal Marlborough, with a lower risk from Taranaki to eastern Bay of Plenty, southwards.

On Friday and into early Saturday there was a risk of snow to 600m in parts of the central North Island and ranges of Hawkes Bay about the Wairoa District late Friday into Saturday. Higher roads in this area were likely to be affected, including the Desert Rd and the Napier to Taupo Rd.

From late Saturday and during Sunday, the southerly flow was forecast to ease as a ridge of high pressure over the Tasman Sea slowly drifted on to the country.

Today's weather

Whangārei

Morning cloud, breaking to a fine day. Light winds. 19C high, 9C overnight.

Auckland

​ Mainly fine. Chance of a shower about the west coast. Westerly breezes. 17C high, 10C overnight.

Hamilton

Cloudy periods. Westerly breezes. 17C high, 5C overnight.

Tauranga

Cloudy periods. Westerly breezes. 18C high, 8C overnight.

New Plymouth Cloudy periods, light afternoon shower or two. Northwesterlies. 16C high, 12C overnight.

Napier Fine. Northwesterlies. 21C high, 8C overnight.

Whanganui​ Cloudy periods, chance morning shower. Northwesterlies. 17C high, 10C overnight.

Wellington A fine start, but cloud increasing in the afternoon. Strong northwesterly, possibly gale in exposed places, easing evening. 15C high, 11C overnight.

Nelson Cloud increasing. Rain developing overnight. Northwesterlies easing. 18C high, 11C overnight.

Christchurch High cloud. Rain developing in the evening as northwesterlies change to cold southerly. 19C high, 5C overnight.

Dunedin Becoming cloudy. Rain developing late morning with a cold southerly change, then clearing overnight. 14C high, 5C overnight.