Another rain watch for top of the south as low-pressure system moves in

Wednesday, 9 July 2025

The rain soaked top of the South Island could see between 100mm and 200mm of rain as another watch is issued for the region.

On Wednesday, the MetService issued a yellow rain watch for 13 hours from 1pm Friday to 2am Saturday, covering Nelson about and southeast of Motueka and north of Lake Rotoroa, as well as Marlborough northwest of the Awatere Valley.

The watch is in addition to one already in place for for Tasman District, northwest of Motueka, for 14 hours from 1pm Wednesday to 3am Thursday.

There is a high chance of the Tasman watch changing to an orange warning, and a moderate chance of the Friday watch upgrading.

MetService meteorologist Devlin Lynden said a low-pressure system was sitting south of Australia and would gradually make its way across, bringing heavy rain to the top of the south and parts of the North Island.

“Come Friday, we’re expecting some reasonable rain accumulations.”

While the forecast could change in the coming days, at this stage there could be rainfall of between 100mm and 200mm across Friday and into Saturday, he said.

“You’re certainly in for another wet period.”

Because the region was already so sodden after record-breaking rain caused widespread flooding at the end of June, there were continued risks from more rain in the area, he said.

“You’re likely to see rivers rise again and potentially, or most likely, surface flooding in areas. It’s hard to say exactly.”

Tasman District Council head of environmental science Rob Smith said they were actively monitoring the incoming rain.

The main rivers were mostly back down with plenty of capacity for more water, but the biggest risk was around smaller streams because the ground was so saturated, he said.

“Water will start to pool quite quickly.”

Smith, who is also a group controller for Nelson Tasman Civil Defence, said people should monitor the forecast and river levels as the next bout of rain unfolded as well as keeping an eye out for cracks and movement in the land, because the saturated ground increased the risk of landslips.

“That’s something we’re quite worried about.”

The region was always vulnerable to rain from the north, and the biggest concern was when it “stalled” over the region, rather than moving through quickly, he said.

“It’s just really, really bad timing that we seem to have a whole lot in a row.”