An intense southerly storm brought high winds, hail and torrential rain to New Zealand's Marlborough, the Wellington region and Wairarapa on Friday.

Police said a person was trapped in a car after a tree fell on the vehicle in the Wairarapa town of Carterton. However, a boy trapped under a tree in Blenheim in Marlborough has been freed, Radio New Zealand reported on Friday.

A search and rescue operation is underway on Wellington Harbor where a kayaker is reported to be in trouble.

Part of a roof has been torn off at St Bernard's College in Lower Hutt and the hall roof has blown off at Samuel Marsden Collegiate School in Karori.

Wellington police said they had twice as many calls as usual in the two hours since the storm hit, and the Fire Service has all its trucks out on the roads attending to storm-related call-outs.

Mini-tornados have been reported in the Wellington suburb of Karori, and in Hutt Valley.

Wellington Electricity Lines Ltd company said disruption was widespread across Wellington and Hutt Valley. Engineers were working to restore power.

Wellington Airport reported delays, but said planes have been taking off and landing.

MetService said wind gusts of close to 140 km were recorded at the waterfront and airport, and in Kelburn.

Police said power lines were brought down around the city, including Lyall Bay and Seatoun.

Earlier, the wild weather hit South Island's eastern coastal town of Kaikoura, where southerlies gusted to 115 kmh and the temperature plunged to 7 degC. A group of nine American tourists had been reportedly trapped out on a walkway in Kaikoura.

No cancellations were expected for the Cook Strait ferry, although a tug was being used to maneuver the vessels in Wellington harbor as a precaution, an Interislander spokesman said.