Weather shock: Severe gales, rain and snow due to hit New Zealand

An unseasonable change is on the way - brought on by two significant storms tracking very near NZ in the Southern Ocean. Image / WeatherWatch

New Zealand's summer is set to be rudely interrupted with severe gales, rain and snow as two storms in the Southern Ocean track near to the country.

The first storm tracks past on Sunday, followed by a second larger storm moving through on Wednesday, says WeatherWatch.

The storms will dredge up an incredibly cold change for summer with daytime highs unlikely to reach double digits in some places.

New Zealand's location on earth means we do sometimes get a sudden dramatic cold change in summer - but WeatherWatch said this one is more potent than most and it comes with severe gales.

Snow flurries will start on the Southern Alps as early as tonight and tomorrow with heavier snow likely with the mid-week southerly change.

While all of the country will get a cool down, the top of the nation will be less exposed, said head forecaster Philip Duncan.

"Auckland will drop down to maybe 19C as the daytime high on Wednesday but it will be the westerly winds that may be of more notice with at least three or four windy days in a row on the way with gusts to gale force at times" he said.

The wind chill will get down to freezing in northern Southland and other areas inland. Dunedin will feel like 6C at noon on Wednesday with an air temp of about 10C or 11C.

Large waves are expected to hit the West Coast of the South Island. Photo / Mark Mitchell

In Fiordland National Park a true wintry change will hit. RuralWeather.co.nz said the daytime high for Milford Sound is currently just 5C on Wednesday as this main southerly comes in. The wind chill factor will make it feel like 1C at midday.

"Trampers, campers and hikers in these areas will need winter gear and be prepared for blizzards higher up in the ranges" said Duncan.

A stormier than usual Southern Ocean since spring 2020 is the driver of this much colder than usual change for parts of NZ, Duncan said.

Starting on Sunday, Wellington has four days of potential gale force winds and regions up to Taranaki will also experience strong winds up to gale force as the air is funnelled through the Cook Strait area. Thunderstorms are possible in the west of both islands too.

Canterbury will be partially sheltered from these systems with temperatures not dropping below the late teens in Christchurch.

Waves of over 12m are expected to crash into the lower half of the South Island's West Coast by mid week and big swells will spread up the west and south of both main islands.