Weather: 140km/h winds, heavy downpours batter New Zealand into chaos

A monster storm in the Southern Ocean is churning up "gigantic seas and hurricane-force winds", bringing dangerous conditions to New Zealand and forcing the cancellation of flights.

A strong wind warning has been issued for Wellington as powerful gusts tear through the capital.

"Northwest gales are forecast to be severe in exposed places at times, with gusts reaching 140km/h," MetService says.

"Strong wind gusts could damage trees, powerlines and unsecured structures. Driving may be hazardous, especially for high-sided vehicles and motorcycles."

Air New Zealand says the strong winds have led to services in and out of Wellington Airport being cancelled until midafternoon today.

"Customers with Wellington flights are strongly recommended to consider deferring non-urgent travel," it says.

"The airline has put on additional services for later this evening to accommodate disrupted customers and will continue to explore additional capacity as the day continues."

Strong wind watches have also been issued for Taranaki, Wairarapa, Nelson, Marlborough and the Canterbury High Country.

Downpours and thunderstorms are also set to blast the country, with rainfall totals of at least half a metre in some West Coast areas.

"The latest thunderstorm risk chart for today shows a high risk for West Coast, including large hail, into this afternoon, then a moderate risk for Southland, Clutha and Dunedin this afternoon," MetService says.

NIWA meteorologist Chris Brandolino says flooding in Westland, Hokitika, Haast, and Franz Josef  is a "distinct possibility".

"That much rain in a short period of time [means] rivers will rise really quickly, so that's something we need to be mindful of," he told The AM Show on Tuesday.

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