People have been forced to flee homes and camping spots, and a boat has washed ashore hampering rescue efforts as wild weather battered the South Island overnight.
Tens of thousands are without power this morning and snow is falling in southern regions.
At Dobson, on the West Coast, a trampoline was picked up and thrown into a powerline, sparking a fire in a transformer.
Roads are closed, blocked by toppled trees and snow drifts, and roofing iron has peeled off homes by storm-force gales.
In the Nelson region freedom campers were forced to flee their Mapua spot when a large storm surge left them stranded in knee-deep water.
The storm has caused major power cuts on the West Coast, Nelson, Marlborough and parts of the South Island's east coast early this morning, says Fire Emergency NZ southern communication's Ian Littlejohn.
"Thankfully there were no reports of injuries."
In the Nelson suburbs of Tahunanui and Monaco firefighters responded to reports of sea surge but were forced to continue on foot when they found Martin St blocked by a catamaran, Littlejohn said.
State Highway 69 between Reefton and Inangahua was closed by fallen trees this morning.
So far more than 15cm of rain has fallen in the Central Otago settlement of Kingston and roads are blocked by heavier drifts and debris.
Meanwhile it has been a stormy night in the capital - but not as bad as initially feared.
Fire and Emergency said the strong wind gusts had brought down powerlines in Wairarapa.
Power is also out to parts of Upper Hutt this morning.
Wellington Electricity said 144 customers in Kaitoke and Te Marua were affected.
Metservice meteorologist Karl Loots said it had been windy and wet across the region.
"Wind speeds peaked at around 4am with gusts around 120km/h.
"We also saw a brief period of heavy rain. The highest rainfall was about 26mm through Wainuiomata."
Loots said on Mt Kaukau the strongest wind gust recorded was 155km/h.
The NZTA has warned motorists of strong winds on the Rimutaka Hill this morning.
• Maximum wind gust: 154kmh at Mt Kaukau in Wellington;
• Most rain in an hour: 33mm at Mt Taranaki,
• 20cm of snow recorded at the Homer Tunnel, Fiordland.