Brace yourself NZ: Tornado rips threw Otago

BREAKING NEWS: A state of emergency nationwide has been declared as gale-force winds tear up the country.

Jade McLellan of Pisa Moorings in Cromwell says a twister ripped through her yard around 11am, tossing a boat across her yard.

"It lifted our pontoon boat off its trailer, flipped it a couple times and then dumped it on our next door neighbours lawn, about 10 metres from their house," she told ONE News.

She saw a few more smaller twisters since then and thunder and heavy rain have been battering the area, she said.

A lightning strike has set a house on fire on the West Coast, meanwhile in the lower North Island, powerful, damaging winds have started to arrive, with worse forecast to come.

Wild weather has battered the lower and western parts of the South Island, causing roofs coming loose, a truck rolling in Dunedin, carnage-causing trampolines to fly up in there air hitting cars.

Emergency services were called to attend to the truck and trailer unit at 12.54pm after strong winds caused it to roll.

"It has created a bit of a mess," the spokesman said.

The driver had been removed and was being attended to by St John staff. It was not yet known how serious his injuries were.

Roofs and outdoor equipment were also causing havoc across the south.

The spokesman said there had been "a few calls about loose roofing".

A trampoline had also blown through a conservatory in Waikouaiti, causing extensive damage.

As the front made landfall in Canterbury, people were urged to prepare for the severe winds and take extra care on the roads.

"And make sure things are secure outside," he said.

MetService has said the front will be preceded by a strong northwest flow, bringing heavy rain and thunderstorms to the West Coast and Otago and Canterbury headwaters.

Up to 250 millimetres of rain could fall within 30 kilometres east of the Southern Alps.

Northwesterlies are expected to rise to severe-gale level for most eastern parts of the South Island. The gales could reach 140kmh about inland Canterbury and the Canterbury Plains north of the Rangitata River.

GALES FOR THE NORTH/ Fairfax NZ

MetService is warning of gusts up to 120kmh overnight tonight with potential to topple power lines and trees.

By 12.30pm today gusts of 100kmh had been recorded at Kelburn in Wellington and the State Highway 2 Rimutaka Hill Rd, between Wairarapa and Upper Hutt, MetService forecaster Dan Corbett said.

But the worst would come late tonight and early tomorrow morning.

"They are going to get stronger and it's going to be a noisy night in Wellington."

MetService forecaster Sarah Garlick said as the ''pretty extreme'' northwest wind increased later this afternoon, so would the temperature, which would peak at about 15degC in Wellington and 16C Wairarapa.

This was because the wind was coming in the form of a ''warm air stream'' from the northwest.

The wind was enough to bring down power lines and trees. Drivers of high-sided vehicles should also be careful, she said.

The wind was fairly typical for this time of the year.

Hawke's Bay was under watch for severe northwest gales later tomorrow, while Taranaki and the Central Plateau are in for potential heavy rain on Thursday.

In Wellington, the powerful wind and relatively warm temperatures would stick around tomorrow, when there could also be some heavy showers, before the wind and heavy rain let up on Thursday.

Fine weather was forecast for Wellington both days this weekend.

Just last week, southerly winds tore through Wellington with 150kmh gusts recorded in Cook Strait and on Mt Kaukau, MetService said.

Gusts of 110kmh were recorded at Kelburn and 100kmh at Wellington Airport.

Damage included a window blown out in central Wellington, a trampoline blown away in Titahi Bay, a tree down in Johnsonville and a roof lifting in Island Bay.

NZTA this morning issued a warning for motorists to beware of high winds on the State Highway 2 Rimutaka Hill Rd, between Wairarapa and Upper Hutt.