West Coasters are bracing for more torrential downpours after a night of rain, with rivers rapidly rising and emergency services poised to respond to the unfolding situation threatening landslides, flooding and the likelihood communities could be cut off.

This morning the Westland District Council said the Waiho River at Franz Josef water level was 7.926m at 8.30am, increasing by 419mm per hour.

The New Zealand Transport Agency (NZTA) warned motorists against driving “unless you really need to” due to the risk of surface flooding.

Sandbags were being handed out on the streets of Hokitika yesterday and Civil Defence staff from across the South Island were pulled in as locals prepared for the massive deluge from an atmospheric river of moisture.

Civil Defence mobilised staff and resources as “a month’s worth of rain in one day” began falling on the West Coast yesterday - and while 80mm had already been recorded, the heaviest downpours were tipped for this morning.

MetService issued the most extreme heavy rain warning for Westland for 47 hours from 9am Thursday until 9am Saturday. Up to 800mm could fall in this time, likely to create “dangerous river conditions” and “significant” flooding.

This morning MetService told residents to expect 350 to 550 mm of rain to fall in the ranges and 50 to 150 mm on the coast. The heaviest rain is forecast from late Friday morning when peak rates of 30 to 35 mm/h are likely.

Parts of the North Island are now under a heavy rain watch for the weekend. Beginning Saturday, heavy rain is likely to fall in Gisborne, Mt Taranaki and the Tasman District west of Motueka.

Meanwhile, Stuff reported Civil Defence had set up a base of operations inside the council building in Hokitika and staff had been pulled in from around the South Island.

Another heavy rain warning is in place for the Grey District and Fiordland from midnight on Thursday to 9am on Saturday; and a heavy rain watch is active in Tasman west of Motueka, Buller and the headwaters of the Canterbury and Otago lakes and rivers.

West Coast Emergency Management (WCEM) said: “Now is the time to prepare for extreme weather,” and the Westland District Council has been giving out sandbags to businesses and residents in Hokitika most at risk of flooding.

Group manager Claire Brown said WCEM had been working with the Department of Conservation (DoC) and as a matter of caution strongly suggested anyone planning to travel in the district tomorrow should keep an eye on weather warnings and take supplies like food and water with them.

Amid West Coast storm, Christchurch tipped for 30C+ days 

Meanwhile, on the east of the South Island, Canterbury’s Medical Officer of Health has urged people to keep themselves cool and hydrated as 30C-plus days have been forecast for Christchurch. 

Elsewhere, Auckland had a cloudy and showery outlook for Friday with a daily high of 28C. Saturday should be a bit cooler at 27C with a chance of a shower and clouds while Sunday could see periods of heavy rain. 

MetService has forecast 30C for Christchurch on Friday and 32C for Saturday. There could be a few spots of rain on both days. 

Dr Matt Reid, the region’s Medical Officer of Health, said: “It’s especially important to stay out of the sun where possible, avoid extreme physical exertion, and ensure pets and people are not left alone in stationary cars. 

“While we are all vulnerable to hot temperatures, some people are particularly at risk. This includes the elderly, infants and children, women who are pregnant and people suffering from chronic, acute and severe illness.” 

‘Follow advice of local Civil Defence groups’ - MetService 

MetService meteorologist Mmathapelo Makgabutlane said the heaviest rain was expected from late on Friday morning, and “when that comes, it will be on top of what’s already fallen”. 

She said people should be mindful if they are camping in the West Coast area, particularly those near water. “And if people have plans to travel there, definitely stay up to date with the latest forecasts and think about making alternative plans.” 

Makgabutlane said: “We’ll be giving regular updates as the weather system continues, and in the meantime, people should follow the advice of local Civil Defence groups.” 

WCEM said the “long duration of heavy rain is expected to be especially impactful for Westland south of Otira, and the rain warning there has been upgraded to a red warning. Please stay up to date with the latest forecast.” 

It said rain could cause slips and flooding, which would likely disrupt travel by making roads impassable and isolating communities. 

The Westland District Council had prepared at least 500 sandbags for locals to use, “but we ask that people only take what they need to protect their properties”. 

“We also suggest that if there is surface flooding, people minimise their vehicle usage in these areas to reduce the bow waves sending water off the road and on to the pavements and surrounding premises.” 

The council has been giving away sandbags on the corners of Stafford and Sewell, Hamilton and Tancred, Trancred and Wells and Weld and Sewell Sts. 

WCEM said: “Agencies and first responders will be meeting this afternoon. There is a high level of concern about possible impacts of the weather, particularly south of Hokitika.” 

An emergency operating centre will be set up tomorrow to help co-ordinate responses to the storm between the WCEM and the district council. 

The National Institute of Water and Atmospheric Research (Niwa) said river flows on the West Coast would be “extremely high” by Friday evening with a “month’s worth of rain in a day” likely to fall. 

“Of particular concern is the Waiho River near Franz Josef due to sediment build-up in the riverbed from previous flooding events.” 

The atmospheric river came from a “moisture plume extend[ing] back to northern Australia, where the monsoon is active,” Niwa said. 

Southland Mayor Rob Scott, whose region could get 350mm of rain over the next two days in Fiordland, said: “The West Coast is going to get a hammering”. 

Raphael Franks is an Auckland-based reporter who covers breaking news. He joined the Herald as a Te Rito cadet in 2022.