State Highway 1 in Marlborough is reopening and evacuated residents from three settlements have been told they can return home from lunchtime on Sunday.

But on the other side of the island, West Coast residents face heartache, with flood-ravaged streets and homes.

The Marlborough District Council said State Highway 1, including the Wairau River Bridge, was expected to reopen from midday on Sunday. "All evacuated residents from Tuamarina, Spring Creek and the Lower Wairau can return to their homes from midday."

Other roads in the region are still closed. SH6 between Renwick and Havelock is not expected to open until mid-afternoon at the earliest and SH63 is not expected to re-open for some days. Many local roads are also still closed.

On the West Coast, residents in Westport have been told to conserve and boil water - and try to stay put - as officials survey the damage wreaked by one-in-100 year floods this weekend.

Thousands of people across the West Coast and Marlborough had been forced to evacuate flooded properties after wild weather thumped the centre of the country.

And although a "code red" weather warning was officially lifted this morning, more heavy rain was expected today.

"We know you are keen to get home, however, due to the risk of floodwater contamination and the potential for electrical hazards, we advise you to stay where you are," the Buller Distrrict Council said in an alert at 8.30am.

As well as being asked to conserve water, the council said residents should boil water as a precaution. "A boil water notice means you need to boil or treat all water from taps/tankers before drinking, brushing teeth or using in food preparation – bringing water to a rolling boil is sufficient to kill bugs."

The Defence Force is sending more personnel to the Buller region to help flood-stricken residents, looking to assist with cordons and accessing hard-to-reach houses.

"We currently have 14 personnel from Burnham Military Camp assisting on the West Coast – this includes Liaison Officers with West Coast Emergency Coordination Centre in Greymouth and the Buller District Emergency Operations Centre in Westport and soldiers assisting with relief work," said a spokesperson.

"Ten additional personnel are on their way from Burnham Military Camp to provide assistance to those current personnel on the ground.

"We are expecting a Royal New Zealand Air Force NH90 helicopter to arrive in Westport by early afternoon to assist in the region."

Meanwhile Waka Kotahi NZ Transport Agency contractors are beginning the hard work of reconnecting those communities cut off by this weekend's massive weather event as flood waters begin to recede.

Journey manager Tresca Forrester said crews have been out since first light assessing road damage, inspecting bridges and clearing debris from blocked and flooded highways.

Access to some cut-off communities such as Westport and through to Golden Bay has been re-established, with the SH67 Buller Bridge, SH60 from Collingwood to Riwaka and SH6 from Hira to Rai Valley all re-opened.

Rai Valley to Renwick remains closed.

Forrester said all available resource is being applied to re-open closed roads as quickly as possible.

"Contractors are aiming to re-open SH1 by midday and we expect to re-open a route through to Nelson by the end of the day via SH6 and SH65," she said.

"We are also assessing flood damage on SH7 north of Hanmer this morning which completes this critical link."

Forrester said until the full scale of the damage caused by the massive floods is known it's too early to say with certainty when other closed roads will re-open.

She is also urging anyone driving in the region to take extra care and be aware that they are likely to encounter surface water and debris on some re-opened roads, with many operating with lane restrictions or under temporary lower speed limits.

"With the massive rainfall we've just experienced, many areas will remain highly susceptible to slips, or to further flooding if the rain returns," she said.

"Please keep safe and take extra care out on the roads today."

Residents in Westport have been told to conserve and boil water - and try to stay put - as officials survey the damage wreaked by one-in-100 year floods this weekend.

Thousands of people across the West Coast and Marlborough had been forced to evacuate flooded properties, while roads and highways remain closed after wild weather thumped the centre of the country.

And although a "code red" weather warning was officially lifted this morning, more heavy rain was expected today.

"We know you are keen to get home, however, due to the risk of floodwater contamination and the potential for electrical hazards, we advise you to stay where you are," the Buller Distrrict Council said in an alert at 8.30am.

As well as being asked to conserve water, the council said residents should boil water as a precaution. "A boil water notice means you need to boil or treat all water from taps/tankers before drinking, brushing teeth or using in food preparation – bringing water to a rolling boil is sufficient to kill bugs."

Evacuations began in Buller, on the South Island's West Coast, on Friday night, when more than 820 people were told to evacuate as heavy rain caused rivers and streams to rise.

Yesterday, evacuations continued - in Westport in the Buller District, Riwaka in Tasman District and in Renwick and several rural communities home to several hundred people between Blenheim and Picton in Marlborough District.

Deputy mayor Nadine Taylor declared a state of emergency in Marlborough at 12.20pm.

Late last night West Coast Civil Defence told anyone in Westport who hadn't yet evacuated to "shelter in place" and call 111 if lives were at risk.

Flood levels in Buller, where a rare "red warning" was issued by MetService on Friday reached their highest level since 1926 at the Buller Te Kuha monitoring station.

The warning was downgraded to orange last night.

Roads out of Westport were cut off yesterday, although the bridges over the Buller and Orowaiti Rivers had reopened this morning.

"Westport is an island at the moment," Buller mayor Jamie Cleine, who earlier described the event as "at least a 50-year flood event", told 1 News. "I've never seen anything like it."

Wairau River Bridge near Renwick in Marlborough is washed over by the flooded river. Photo / Marlborough Distirct Council

Niwa tweeted at 7pm that the Buller River level was just below 12.4 metres, down from its peak earlier in the day of 12.8m.

Floodwaters proved dangerous for some, with several motorists rescued from stranded vehicles, including five people in two vehicles at Tuamarina, north of Blenheim.

A front-loader helped others, and a person was plucked from the roof of a flood waters-surrounded campervan by helicopter at Woodstock in Tasman district's Motueka Valley.

Meanwhile, in Hunterville, north of Palmerston North, two were hurt - one seriously, one moderately - when a tree fell on their car at 4pm, trapping them.

Fire and Emergency cut the pair out and they were taken by St John Ambulance to Whanganui.

A state of emergency was declared on the West Coast. Photo / George Heard

Although the worst of the weather was in the upper South Island, other parts of the country didn't escape the mid-winter blast.

Heavy winds battered Taranaki, where at least one trampoline took flight and those posting to the Extreme Weather Taranaki Facebook page reported shaking windows, a porch being blown out and waves crashing over a rock wall at Port Taranaki.

"When is this wild weather due to go away? Feels like my house is going to blow away," wrote one.

In Wellington, roofs were ripped off overnight yesterday and by midday Wellington City Council had received "more than 20 calls to reports of flooding on roads and into private properties", as well as shops in Berhampore.

Three state highways were closed because of flooding, and others had lanes blocked.

Heathcliffe the horse had a lucky escape. Photo / Rob Suisted, www.naturespic.co.nz

A horse named Heathcliffe had a lucky escape after he became trapped in the flooding Takapu Valley stream. Brave residents - including newly retired Wellington police launch skipper David "Tex" Houston and well-known teen powerlifter Rachel Duncan - risking their lives to first keep the horse's head above water and later help as a digger hauled the animal free.

Owner Yvonne Denton said last night the "treasured family horse" had been checked by a vet and was doing well in a neighbour's stable, but they had to watch for pneumonia as the 21-year-old Cleveland Bay X had water in his lungs.

"His head was under water [when Duncan arrived]. She jumped the fence and literally pulled his head out of the water. I can't thank everybody involved enough."

It also wasn't a good day for travel yesterday.

As well as closed roads and highways, some ferry services in Auckland were cancelled and 28 domestic flights disrupted.

In the worst affected areas - Marlborough, Nelson, Westland and Buller - periods of heavy rain, with heavy falls and thunderstorms, would ease this morning, MetService said.

MARLBOROUGH DISTRICT

ROAD CLOSURES:
• SH 1 Picton to Spring Creek. Flooding.
• SH 63 Renwick to St Arnaud. Adverse weather.
• SH 6 Motupiko to Kohatu, between Korere Tophouse Rd and Motueka Valley Highway intersections. Flooding.

EVACUATED TOWNS:
• Tuamarina
• Spring Creek
• Lower Wairau
• Renwick Lower Terrace

HELP INFO AND UPDATES: https://www.marlborough.govt.nz/services/alerts

BULLER DISTRICT

ROAD CLOSURES:

• SH 67 Fairdown to Mokihinui. Flooding, slips.
• SH 6 Inangahua to Westport - Lower Buller Gorge. High river levels
• SH 6 Murchison to Inangahua. Water across road at Dee Creek
• SH 65 O`Sullivans Bridge to Shenandoah. Flooding, multiple slips.
• SH 7 Springs Junction to Reefton - Rahu Saddle. Slip.
• SH 7 Hanmer Turnoff to Springs Junction. Flooding.

EVACUATED TOWNS:
• Westport, with those still home told to shelter in place

HELP INFO AND UPDATES: https://bullerdc.govt.nz/district-council/news/severe-weather-event-updates/