The terrible weather which has pounded the South Island today is set to ease tomorrow, but not before one more lashing over Nelson and Buller.

Communications in and out of South Westland were completely cut off this morning when a chunk of the Wanganui Bridge, just north of Harihari, was ripped away.

The only fibre optic cable to the area, which ran along the bridge and which about 1000 South Westlanders rely on for phone and internet use, was also cut when part of the bridge disappeared into the river.

Technicians were on their way to the site to begin reconnecting the cable, which would hopefully be completed overnight.


MetService forecaster Andy Downs said the rain was easing in Westland, and would decrease "fairly rapidly'' this evening.

But the concern now was around north-west Nelson and Buller.

A heavy rain warning was in place for the region, and a band of thunderstorms had also been triggered, he said.

"They could actually increase the rain rates up towards the torrential levels, 40mm plus per hour. If that happens you can start getting flash flooding on top of everything else.''

Earlier today, 120 trampers trapped in Milford Track huts for two nights were able to walk out after the Department of Conservation reopened the walking track in Fiordland National Park.

Police were also warning people in areas along the Rakaia River in the Selwyn District of Canterbury to evacuate as the river continued to rise.

It was overflowing onto State Highway 72, and motorists were also warned to stay away from the area.

Strong winds have been lashing inland Canterbury, Marlborough, Wellington and Wairarapa. The summit of Mt Hutt experienced wind gusts reaching 200km/h.


A handful of flights scheduled to land at Wellington Airport had to be cancelled or diverted today because of gusts up to 140km/h.

One flight had to turn back to Auckland after it was not able to land due to the wind, an airport spokeswoman said.

The high winds were expected to move up the lower North Island overnight.

But as the front, which has been bringing winter-like weather to the south, moved up the country it would ease, Mr Downs said.

"The good news, which of course we all need now, is that there's a ridge of high pressure following in behind this, and that is set to sit over central New Zealand right until Sunday.''

"So once this front has cleared the country tomorrow morning, we're really looking at an improving trend.''