Sand bags are being placed around businesses in Wanaka as the rain continues to pour.

Heavy rain hammering the West Coast has caused a slip north of Haast, closing State Highway 6 until at least midday Friday.

The highway was closed just before 3pm on Thursday at Knights Point, between Fox Glacier and Haast, following a heavy slip and fallen trees.

An update on the closure is expected at 12pm on Friday.

Supplied Torrential rain has caused slips and fallen trees to block SH6 near Knights Point.

Metservice meteorologist Tahlia Crabtree said record amounts of rain had fallen in recent days, even for West Coast standards.

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"More than 600 millimetres of rain has accumulated at several weather stations in the Alps since Monday, which has then flowed from alpine headwaters into rivers and lakes.

Supplied The highway will be closed until at least midday on Friday.

"The persistent rain means lakes and rivers haven't had the chance to subside."

Heavy rain warnings were out and expected to continue until Sunday, she said.

In Otago, more than 2000 sandbags were sent to Queenstown, Wanaka and parts of Central Otago on Wednesday in advance of possible flooding.

DEBBIE JAMIESON/STUFF A small sail boat tethered to a tree, which is usually on the bank at Frankton beach in Queenstown, under water on Thursday morning.

The Queenstown Lakes District Council (QLDC) also closed off part of Wanaka's main lakefront street and a 30kmh speed limit was in place across the entire Wanaka CBD.

The sewer connection to some premises were been shut down temporarily to mitigate the potential for sewage to enter the lake.

MetService is forecasting large downpours throughout Otago for the rest of the week.

YOUNG ADVENTURES The water at Wanaka has flooded footpaths along the shore.

QLDC general manager property and infrastructure and acting controller Peter Hansby said staff and contractors were continuing to assess the potential effect on stormwater and wastewater networks in high risk areas.

Both Lake Wanaka and Lake Wakatipu were expected to peak at predicted levels by Sunday, he said.

"Both lakes are expected to peak well below the 1999 flood levels. The [Otago Regional Council] has confirmed that rain has eased in the headwaters and the long-term (10 day) forecast does not contain significant rainfall."

Otago Regional Council Floodwater from the Dart River spilling into Lake Wakatipu at Glenorchy.

According to ORC data, Lake Wanaka's water level was 279.968 metres on Thursday evening, just above the high lake level but below flooding level. Lake Wakatipu was at 311.191m, just below flooding level.

The heavy rain forced 224 Wakatipu High School students and staff to be evacuated from a camp at the remote Branches Station, and two course changes for the off-road Pioneer bike race.

Snow, and high wind made it impossible for the 380 riders to climb the Carrick Range, near Cromwell on Thursday, spokesman Andrew Dewhurst said.

YOUNG ADVENTURESS Wanaka's famous tree is more underwater than usual.

The ride up Mt Difficulty was also removed as the weather deteriorated further and temperatures plummeted to minus 3 degrees Celsius across the top of the climb.

The end result was one of the fastest stages in the history of the six-day mountain bike race, covering 61km with about 1182m of climbing, he said.

The Catch Wanaka manager Johnny Shea said the town's lake had "definitely risen" and the car park by the lake across the road from the shops was nearly flooded.

YOUNG ADVENTURES Flooding at the shoreline in Wanaka.

"[The water's] still in the car park across the road, it's about 30m from [us]," he said.

"It's come up about 20m closer to the township."

Waiting for the floods was "purely a waiting game" and "like watching paint dry", he said.

It is a family and community effort sand-bagging four-day old business The Catch Wanaka. Pictured is (from right): manager John Shea with owner Ian Warner, Georgia Warner, Marion Warner, Brian Warner, Stefan Grant and Foley Plumbers Wanaka workers Jordan Wood and Brett Jarvie.

"I guess it's up to mother nature, we can't do anything."

Up to 80mm of rain was expected around the Otago lakes and rivers on Thursday, with more expected on Friday.

In Central Otago, a boil water notice was in place for residents and visitors to Alexandra, Roxburgh and Lake Roxburgh Village on town water supplies until further notice.

Riccardo Testoni A video taken on the trail next to Queenstown's Hilton Hotel on Tuesday shows how high the water in Lake Wakatipu had become, with parts of the trail already flooded.

The council's Facebook page has a list of locations where water tankers will be situated.

Strong wind warnings were in place for the Marlborough region and the North Island's Wairarapa and Tararua districts.

Flooding had also closed SH63 in Marlborough's Wairau Valley.

The country's main centres experienced generally fine weather.

Auckland had a fine day with a high of 25C, strong winds and rain, while a high of 18C was recorded in Wellington, and 24C in Christchurch.