Three tornadoes, hail as big as a tennis ball and 2000 lightning strikes were reported on the West Coast yesterday -- with another front forecast to strike later today.
Civil defence group leader for the West Coast, Chris Raine, said forecasters expected the weather to go downhill again early afternoon, with the rest of the day to be marked by thunderstorms, strong winds, hail and coastal tornadoes.
The thundery weather yesterday afternoon spawned an impressive tornado just north of Ross.
Sam Wanrooy captured the moment from Butlers farm, looking towards the Tasman Sea.
"Lots of trees were taken out and [they] lost some windows and equipment at the gold claim," Mr Wanrooy said.
Geoff Cook was inside the farmhouse at the time, and saw it come off the sea and cut across the farm, throwing corrugated iron and gorse into the air.
"It took a couple of windows out of some work vehicles," Mr Cook said.
Mr Raine also had reports of smaller twisters at Rutherglen yesterday and again overnight, with trees reportedly felled and the road temporarily closed.
About an hour before the Ross tornado, at 3.07pm, the Metservice weather radar detected severe thunderstorms near Kakapotahi and Lake Ianthe.
Nearby, Pukekura experienced a 30-minute hailstorm that stopped traffic on State Highway 6, accompanied by a massive thunder and lightning exhibition.
Peter Salter from the Bushman's Centre said hail the size of golf balls and bigger rained down about 3.15pm.
"I was worried about our car outside -- massive, massive hailstones coming down, some of them even the size of tennis balls."
A huge electrical storm with sheet lightning lit up the night sky at Greymouth for about 30 minutes until about 7 o'clock, although a number of people who watched the spectacle said they did not hear thunder.
The Metservice counted 2000 lightning strikes in Westland since yesterday, noting that a lot of these were out at sea.
In Greymouth, thick foam at least chest height coated the Blaketown-Karoro section of the cycle trail.
Haast Pass was closed overnight and this morning due to fallen trees across the highway.
Mr Raine said the civil defence watch had now moved to Karamea. River wardens were checking the situation and liaising with local residents and farmers.
High winds closed the Arthur's Pass highway around teatime last night, and State Highway 6 from Murchison to Inangahua was down to one lane this morning due to fallen trees.
The NZTA said there were also minor rockfalls around the Rock Shelter and Rocky Point at Otira, and several slips on the Coast Road. At Ten Mile, the road was down to one lane for a while. At lunchtime, a logging truck rolled at Porters Pass, blocking both lanes of State Highway 73.
- Greymouth Star