Wellington, March 12 NZPA - High winds blew over trees and power lines, and swamped emergency services in Wellington and Kaikoura as atrocious weather shunted up the east coast this afternoon.

Several people also received minor injuries, including a teenage boy hit by a falling tree branch at Rarangi near Blenheim, in Marlborough.

Wind gusts of nearly 150kmh were recorded on Mt Kaukau, and the temperature dropped from 19.9degC to 9degC when the "aggressive" southerly front reached Wellington late this afternoon, weather analyst Philip Duncan said.

Winds gusted over 120kmh elsewhere in the city, causing damage to roofs and powerlines, and bringing hail.

Earlier, the wild weather hit Kaikoura, where southerlies gusted to 115kmh and the temperature plunged to 7degC.

No sailings were cancelled for the Cook Strait ferry, although a tug had been used to manoeuvre the vessels in Wellington Harbour, an Interislander spokesman said.

In Wellington, power lines had been blown down from Island Bay to Upper Hutt and across to Paekakariki on the Kapiti Coast, a Wellington Electricity spokesman said.

Power companies had been flooded with calls, and engineers were working frantically to restore power and remove fallen lines.

A woman was trapped in Carterton when a tree fell down across her car, causing minor injuries, Inspector Ian Harris said.

The police launch was called out to rescue a kayaker about 4.30pm near Oriental Bay, but after several hours' searching it appeared to have been a yellow racing buoy, Mr Harris said. There had been no reports of an overdue kayaker.

Conditions on the harbour were described as "atrocious" by the Wellington Coastguard, which was helping police.

The weather also caught out yachts taking part in an annual fundraising race by the Royal Port Nicholson Yacht Club. Eighty-two business people -- including celebrity chef Martin Bosley -- were racing around Somes Island and back on members' boats.

Thirteen keel boats took part, with three needing to be towed to shore and three having to wait out the storm, yacht club chief executive Dean Stanley told NZPA.

The course had been shortened because of the weather.

One person fell overboard but was quickly rescued.

"We get plenty of wind every now and again in Wellington, and that comes through in fronts, and that was certainly a very intense front," Mr Stanley said.

Police said one yachtie was taken to hospital.

There were also reports of boats in trouble on Porirua Harbour, but they had rescued themselves before police arrived.

Roofs were also blown off buildings at St Bernard's College in Lower Hutt and Samuel Marsden College in Wellington, which was hit by a mini tornado, Radio New Zealand reported.

Earlier, a group of nine American tourists had been reportedly trapped out on a walkway in Kaikoura, 181km northeast of Christchurch.

A 15-year-old boy hit by a tree near Blenheim was flown to Wairau Hospital with lower leg and suspected spinal injuries, a Summit Rescue Helicopter pilot said.

Trees fell across rail lines in Wellington, blocking the Hutt Valley line north of Waterloo station and damaging the overhead power and signalling, a KiwiRail spokesman said.

Crews were working on the damage, although it was unknown when the repairs would be completed.

Trees were down across roads, but the only road completely blocked was Paekakariki Hill Road.

The front had moved north this evening, and the weather was expected to improve by overnight.