Weather: Both islands set for heavy snowfalls as temperatures plunge

Both the North and South Islands are set to get heavy snowfalls as a blast of cold air forces temperatures down.

WeatherWatch says a cold change is "about to pounce" - and it could see as much as 50cm of snow hit the summit of Mt Ruapehu in coming days.

"Temperatures will drop across the country, starting as early as Sunday in Southland and reaching Northland by Tuesday. It's not a majorly dramatic cold change, but it will mix with the extra moisture we have around New Zealand at the moment and that means rain will turn to snow at higher altitudes," WeatherWatch says.

"The North Island's Central Plateau will also finally get a decent dusting of snow, as will Mt Taranaki. On the summit of Mt Ruapehu there may be as much as 30 to 50cms of snow accumulating in the coming days.

"State Highway 1, the Desert Road, may also have its heaviest snowfall of the year so far with traffic potentially affected for a time. Snow may also impact the South Island's alpine passes."

WeatherWatch says this is "very positive news" for the ski industry - especially the South Island’s ski fields.

"The cold air next week will lock in the snow too and create ideal conditions for snowmaking at night too, for those fields with the capabilities," it says.