Severe rain and 140km gales hammer the upper South Island as Takaka Hill records 275mm overnight

A rapidly deepening low has dragged a band of severe weather across the upper South Island and West Coast, with parts of Golden Bay already recording more than a quarter of a metre of rain overnight and MetService warning the worst is still to come on Friday afternoon and through into Saturday morning.

The most extreme totals so far have fallen on the ranges above Tākaka and the lower Richmond Range, where between 150 and 275 millimetres of rain were measured overnight Thursday into Friday, according to RNZ. Further totals of 120 to 180 millimetres are forecast on top of those readings before the system clears, with the Richmond Range expected to take an additional 250 millimetres in the worst of it.

MetService has issued orange heavy rain warnings stretching from Westland and Buller across the Grey district, into the Tasman district northwest of Motueka, and through the Nelson and Marlborough ranges. The warnings extend into the Canterbury headwaters south of Arthur’s Pass and across Nelson Lakes National Park. According to 1News, the longest of the warnings runs for 17 hours over Westland, expiring at 3am Saturday, while the Canterbury headwaters warning runs through to 2am Saturday.

Westland and the Canterbury headwaters are the next focus for the heaviest rainfall, with up to 220 millimetres expected at peak rates of 30 millimetres an hour. Buller and Grey districts are forecast to take up to 130 millimetres at 20 to 30 millimetres an hour, while the ranges in the Tasman district could see another 120 to 160 millimetres on already saturated ground.

The wind side of the system is just as ferocious. Severe gale north-westerlies are forecast to gust to 140 kilometres an hour in exposed parts of the Canterbury high country, the Kaikōura coast, Marlborough, Wellington and Taranaki. Canterbury high country is expected to see sustained gusts at 130 kilometres an hour, enough to bring down trees and disrupt power lines across a wide area.

That has already started happening. Network Tasman reported a single fallen tree had taken down power lines on Wakapuaka Road, leaving around 400 homes in Cable Bay, Teal Valley and Kokoroa without electricity. Crews were working to restore supply on Friday morning, but more outages are expected as the wind peaks during the afternoon.

Roads across the region are also feeling the strain. The Maitai Valley Road has been closed from Ralphine Way after the Maitai River reached capacity and began flowing across low-lying paddocks. Surface flooding has been reported along the route between Nelson and Renwick, and the New Zealand Transport Agency has warned of a flooding risk on State Highway 6 between Makarora and Haast. State Highway 67 north of Westport has also seen flooding, and motorists are being warned that water may cross State Highway 60 at Waitapu Splash and State Highway 6 near Kohatu as the rain continues.

Several rivers are now in moderate flood. The Tasman District Council has flagged the Tākaka, Wai-iti, Wairoa and Motupiko Rivers as the most likely to break their banks in the next 24 hours. The Maitai is already running at capacity, and any further heavy rain in the Maitai catchment will push it over.

MetService meteorologist David Miller said the picture for Friday and into Saturday was straightforward and unwelcome. “We’ve had some heavy rain in the ranges of the Tasman District and Westland on Thursday,” he said. “Heavy rain is expected to continue in these areas right up until Friday evening.”

The active warnings are stacked back to back. The Tasman district north-west of Motueka has a 10-hour rain warning running from 9am to 7pm on Friday. Buller and Grey have an identical 10-hour window over the same period. The Nelson and Marlborough ranges are covered by a 12-hour warning ending at 9pm. Westland’s 17-hour warning is the longest active block. Strong wind warnings cover Wellington, Taranaki, Marlborough and the Canterbury high country, with additional watches in place for Wairarapa, Tararua, Christchurch, Nelson and Tasman.

The system is forecast to ease from the south early on Saturday morning, but heavy showers will continue into the weekend across the West Coast. Once the bulk of the rain passes, the focus will shift to swollen catchments, with rivers across the Nelson and Tasman regions likely to take several days to come back down.

For households in the warning zones, the standard preparation advice still applies. Check that drains and gutters are clear before the rain peaks, secure any outdoor furniture or trampolines that could be picked up by 140 kilometre an hour gusts, and keep a torch and a charged phone within reach in case the power goes off. Anyone driving in the warning areas should slow down, leave more following distance and turn around at any flooded ford rather than trying to push through. Drivers crossing the alpine passes are being asked to delay travel where possible, with both the Lewis Pass and the Haast route exposed to landslip risk during prolonged rain on this scale.

The wider question for the Nelson-Tasman region is how much the ground can take. Several catchments north of Motueka are still recovering from the August 2022 floods, with the rebuild of damaged forestry and rural roads not yet complete in places. A second 200-millimetre dump on top of an already wet autumn raises the risk that smaller streams will break out into properties that escaped damage in earlier events.

Have you been affected by the storm in Nelson, Tasman, Westland, Buller or the Canterbury high country? Are the roads near you holding up, or have you lost power? Share your story and any photos in the comments below so we can keep an eye on conditions across the regions as the system tracks east.

This article was written by AI, briefed to report the facts, hopefully without some of the bias people bring to the job 🙂