The 'bomb low' forecasters have warned Kiwis about is beginning to show its full force in parts of the country on Wednesday night.
MetService says the Southern Alps and the West Coast have been hit by torrential downpours. Mt Cook has had 160mm in the last 24 hours, and one station in the Southern Alps has recorded 31mm in one hour.
A wind warning has been issued for Wellington. The highest measured gust is 118km/h, and 148km/h has been measured at Cape Turnagain.
A severe warning for Canterbury north of Ashburton and Marlborough is in place, with wind speeds expected to reach over 150km/h.
High winds are causing trouble on coastal roads on the West Coast, and tore down a tent at the Pike River protest camp.
Pike River widow and West Coast local Anna Osborne says the weather is extremely bad.
"We have got torrential downpours here. The wind has picked up and it's gale force. We've actually had our tent at the picket line and the gazebo go flying, and we've got streams and creeks that are at their maximum capacity," she told RadioLIVE Drive.
"It's actually really, really horrible to be honest; it's not a nice night to be out on the roads either."
However she says the Pike River protesters will stay - but in the onsite caravan.
'Heaviest is yet to come' - MetService
Despite rainfall arriving on cue, the heaviest is yet to come, MetService meterologist Lisa Murray said on RadioLIVE's Drive show on Wednesday.
Surface flooding is now developing along the coast and inland between Hokitika and Greymouth, forcing road closures.
Heavy rainfall has fallen along the West Coast, where 50mm and 70mm of rain fell overnight in Hokitika and Greymouth, while up to 100mm of rain fell on Arthurs Pass.
Wellington public transport stopped
Trolley buses in Wellington have been cancelled as the Capital battens down the hatches for the weather bomb hitting New Zealand on Wednesday.
Services are being replaced by diesel buses, Metlink says, and it is not expecting any major disruptions to its rail timetable.
Preparing for high winds
MetService is advising the public in the affected areas to tie down and loose outdoor furniture or tools before the wind arrives.
They also advise keeping all windows and doors closed unless necessary. High-sided and light vehicles such as motorbikes and vans are encouraged to park in garages and out of the wind so they don't blow away or cause damage.
Public transport can expect delays or cancellation over the next two days.
Authorities are warning motorists to check the weather forecast before they travel and to adhere to warnings and signage.
Boaties urged to stay off the water
Southlanders have been warned to stay away from the water until the forecasted storm has passed.
"Unless absolutely necessary, stay off the water until the significant weather event has passed," says Southland harbourmaster Lyndon Cleaver.
Mr Cleaver is also asking boaties to check their equipment around Stewart Island and Bluff and make sure their boats are secure.
Wind gusts up to 130km/h are expected in Southland, Fiordland and Stewart Island over the next two days.