Towering seas, punishing gales and heavy snow and rain are lashing central New Zealand as the vicious winter storm enters its third day. 

Snow is continuing to fall across both islands and not expected to let up until tomorrow.

Police describe the gales, rain and snow as a "trifecta of trouble".

Scores of roads across the South Island have closed and eastern and southern parts remain snowbound.

 

Snow at National Park (Video: Supplied).

The North Island is now bearing the brunt of the storm with waves as high as 8m surging through Cook Strait and winds of 140 km/h pounding the region.

• 'A significant, severe winter storm'

Flights in and out of the capital have been disrupted. Snow is falling on the Rimutaka Hill Rd but remains open for now.

Snow is expected to fall as low as 300m in parts of the North Island today.

MetService meteorologist Mark Todd said eastern and central regions of the South Island would continue to be affected by widespread snow showers for the next 24 hours.

Storm lashing central NZ. Gusting over 140km/h Mt Kaukau and Brothers Island. https://t.co/qHyE5zhh6X ^JR pic.twitter.com/ceQ0iSvrQS

— MetService (@MetService) July 12, 2017

The worst affected areas were inland, mid and north Canterbury and Kaikoura where heavy snow was expected down to 200m.

"In this area we expect the showers to start will still easing slowly later today and the snow level to rise gradually but the snow showers will still persist overnight into Friday," said Todd.

Good news for the far south with few snow showers expected across the lower South Island as the weather starts to improve from the blast.

But the focus was now firmly on the lower half of the North Island with the low deeping overnight and rain intensifying across the island.

"We're expecting snow to fall possibly as low as 300m in some places. It's currently snowing on the Rimutaka Hill Road and we have a warning for possible heavy falls of rain and snow falls at high levels for Wairarapa, including the Tararua District, Wellington, the Kapiti Coast and the Manawatu Ranges."

At the same time gales were lashing much of the country early today.

"Cook Strait, we have storm force winds. They're averaging around 100km/h at Brothers Island with occasional gusts to 140km," said Todd.

"The waves at Bearing Head on the Wellington south coast are currently averaging about 5m. The largest waves are between seven and eight metres."

Wellington Airport had already cancelled six flights and many more delayed as the runway was buffeted by wind gusts of up to 90 km/h.

At 6am the Desert Rd was the only major highway closed due to snow.