The first of the wet weather has arrived in Northland this evening as a band of rain begins its journey down the country.

It's expected to continue raining in Kaitaia until midday tomorrow. Later tonight vast swathes of New Zealand are set for a drenching, as a complex low conjures up days of rain, thunderstorms, gales and even snow for the South Island.

The MetService has this evening issued snow warnings for South Island roads, where snow showers are expected on Arthurs Pass, Lewis Pass and Porters Pass from now until Friday morning.

Up to 8cm of snow may settle on Porters Pass and 3-5cm on Arthurs Pass. Lesser amounts are expected to 800m. Lewis Pass could see 1-2cm of snow.

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This morning the MetService put out severe wind and rain alerts covering the upper North Island and southern Westland.

Even before the worst of the weather struck, commuter ferry sailings across Auckland's Waitemata Harbour were suspended today because of blustery conditions.

MetService said the rain was expected to become heavy tonight. The most intense falls were reserved for Westland south of the glaciers, where 100-120mm of rain was expected to accumulate in a 15-hour period. Trampers have been warned to watch for rapidly rising rivers and streams.

However, the Bay of Plenty and Gisborne regions were also expecting to be saturated with up to 100mm of rain falling over 18 hours from 9am tomorrow with thunderstorms in the mix.

Watches for heavy rain and gales were also issued for Northland, Auckland and Great Barrier Island, as a low and associated front approached the top of the country from the north Tasman Sea.

Satellite image showing a large weather system to the north of New Zealand that will bring heavy rains and storng winds to the North today. Picture / NASA
Satellite image showing a large weather system to the north of New Zealand that will bring heavy rains and storng winds to the North today. Picture / NASA

The weather is expected to drastically deteriorate as the moisture-laden front bringing northeast gales and rain starts to unleash its wrath.

Severe gales are likely to pound the Far North today, and the entire upper half of the North Island will be buffeted tomorrow. The gales are not expected to die down until Friday.

Niwa is expecting up to 62mm and 60.8mm of rain to fall in Whangarei and Kaitaia tomorrow, and 21.8mm for Auckland.

MetService meteorologist Andy Best said along with the winds it would be extremely wet along the eastern coastline of both islands, and the West Coast of the South Island, as moisture-laden tropical air caught up in the complex low moved south.

By tomorrow virtually the entire country will be under a storm cloud.

Bay of Plenty, Auckland, Northland and Canterbury are expected to be the worst affected.

Snow was also expected to fall down to 500m in Canterbury tomorrow and Friday, affecting alpine roads for the second week running.

Those at Treble Cone will be hoping the prized flakes head their way too - the Central Otago ski area was to open for the season tomorrow, but that has been postponed due to lack of snow.

The stormy weather is expected to track across the country on Friday but will be followed by a chilly southwesterly change sweeping up the country over the weekend, Best said.

But before then, the upper North Island would bask in spring-like temperatures thanks to the tropical air spilling from the complex low.

"For this time of year it's still warm. Just a day after midwinter's day it'll be 18C in Auckland."

Ironically the West Coast and Fiordland looked like the driest areas for the last day of the working week.

The weather is expected to clear across the rest of the South Island for the weekend to leave cold, frosty mornings.

Outlook

WHANGAREI

Today: Showers turn to rain, heavy from evening. NE rising to gale afternoon. 17C

Tomorrow: Rain, with heavy falls, turning to showers morning with gale NE easing. 20C

AUCKLAND
Today: Cloud increases, evening rain. NE rises to gale, gusting 90km/​h in exposed places at night. 16C
Tomorrow: Rain, chance heavy, turns to showers. NE gale gusting 90km​/​h in exposed places, easing afternoon. 18C

HAMILTON
Today: Morning fog clearing. Cloud increasing from afternoon. 15C
Tomorrow: Periods of rain from morning, turning to showers evening. NE winds, strong at times. 16C

TAURANGA
Today: Cloud increasing, a few showers from afternoon. Northeasterlies. 16C
Tomorrow: Rain develops morning, chance heavy. Showers late evening. NE strengthens for a time. 18C

Several weeks of settled weather around the Kapiti Coast come to an end tomorrow. Photo / Mark Mitchell
Several weeks of settled weather around the Kapiti Coast come to an end tomorrow. Photo / Mark Mitchell