Severe weather which hit the South Island, closing roads and causing power outages, is moving north and is set to hit Wellington in time for Saturday's rugby match between the All Blacks and Argentina.

Parts of Otago and Southland have been hit with gusts of up to 120km/h on Thursday morning and these are expected to spread to Canterbury and Marlborough later in the day, according to MetService.

Severe gusts will hit Wellington and the Wairarapa from Thursday to Sunday.

Heavy rain is expected on the West Coast and Southern Alps on Thursday afternoon until midday Friday with up to 200mm of rain in Fiordland and parts of Westland. More rain is expected on Saturday.

"There are two weather systems moving north... so hold on to your hats as some pretty severe weather comes through," MetService meteorologist Daniel Corbett said.

A police southern communications spokesman told NZ Newswire high winds had uprooted some trees in the West Coast town of Whataroa but no other damage had been reported.

Some homes are without electricity after power lines toppled in high winds in the Clutha region, although a PowerNet spokesman could not immediately confirm the extent of the damage.

State Highway 6 from Haast to Hawea will remain closed until at least Thursday afternoon following a major slip about 2am on Thursday, a New Zealand Transport Agency spokesman told NZ Newswire.

Rocks up to 10 metres long have come down onto the road and more rocks may follow.

SH94 from Te Anau to Milford Sound is also closed due to heavy snowfall on Wednesday night. It is likely to remain closed until Thursday night or Friday morning due to the risk of an avalanche.