Collapse Bridge
© Hokitika Guardian
A central section of this bridge near Harihari on the West Coast was carried away by the storm-swollen Wanganui River.
Gale force winds, torrential rain, thunderstorms and now unseasonable snow have pounded the South Island.

Snow fell on the Lindis Pass in Otago overnight, forcing travellers to abandon their vehicles near the summit.

Sergeant Mark Booth of southern police communications said Lindis Pass was closed and eight vehicles were stranded.

"But I imagine at this time of year the snow's not going to last long."

The centre of the island and the West Coast have "copped it" over the last few days, Mr Booth said.

The West Coast road via Lewis Pass through Murchison had closed, forcing travellers to make a seven hour detour around Blenheim and Kaikoura to get to the east coast of the island.

Last night severe thunderstorm warnings were issued for the Westport area as the last of the system moved through.

Nearly 600mm of rain has fallen on the West Coast in the past 48 hours.

A vital one-lane bridge on State Highway 6, just north of Harihari, was washed away yesterday.

New Zealand Transport Agency West Coast area manager Mark Pinner told Radio New Zealand the road could be rebuilt, but engineers still had to check if the bridge pylons were undermined.

He said that at best it would open tomorrow, but this could take longer if the bridge's foundation had been damaged.

The Old Waimakariri Bridge, near Kaiapoi, has been closed due to high river levels.

It was closed last night and is expected to reopen by the end of the week once the water level subsides and the structure can be checked.

Christchurch City Council advised motorists that the closure did not affect the main Waimakariri Bridge on State Highway One.

Central and northern areas of the North Island were today likely to see some rain with possible heavy falls and there was also a chance of a heavy shower or thunderstorm developing over isolated areas across eastern South Island regions, WeatherWatch.co.nz said.

West Coasters would likely see further showers today. However, the bulk of the rain had now moved north and disbanded a little.

"There's been a tremendous amount of rain and (we are) are surprised there weren't further issues," weather analyst Richard Green said.

"For this amount of rain to have fallen over a relatively short period of time we're thankful that more people weren't caught up in the serious weather conditions," he said.

Half metre of rain has fallen over parts of the West Coast and well over 400mm of rain in Milford Sound where about 120 trampers had been caught out and stranded by the weather.

Rivers east of the Alps had also risen quickly with both the Waitaki and Rangitata rivers filling quickly, but today should see the rivers recede.

Tomorrow and the weekend are looking brighter for much of the country with only isolated showers in the northeast and far south of the country.

Temperatures should be warm to be very warm over many areas on Saturday and Sunday and beaches, lakes and rivers could be the best places to cool off.