New Zealand weather: Heavy rain warning issued for South Island due to atmospheric river

Heavy rain warning has been issued for parts of the South Island, New Zealand. The weather pattern started late Wednesday (March 31, 2025) and by late Thursday moved to the North Island of the country.

An atmospheric river is bringing a significant amount of moisture from the tropics, fueling a low-pressure system and potentially causing flooding and slips. Buller and Tasman districts in the South Island could receive a month's worth of rain in 48 hours. The heavy rain is expected to impact the western and northern regions of both islands. MetService and NIWA have advised residents to clear drains, avoid low-lying areas, and drive cautiously.

The warning have been issued for the Westland District ranges, Buller district, Tasman northwest of Motueka, Nelson Lakes, Bryant Range, Rai Valley, and Marlborough ranges northwest of the inland Kaikoura Range.


“Many areas probably in these regions seeing a couple of hundred millimetres or more of rain over 48 hours, so yeah this’ll be some pretty beefy rain for that region.” The rain is expected to move up over the North Island later in the week," said NIWA principal scientist Chris Brandolino.


MetService meteorologist Mmathapelo Makgabutlane explained that an atmospheric river is responsible for the heavy rain and strong winds. "The main message is that we are expecting quite a lot of rainfall coming in the coming days.”

Specific timings for the heavy rain include 10 pm Wednesday for Westland District ranges, 3 am Thursday for Buller district and Tasman northwest of Motueka, 11 am Thursday for Bryant Range, Rai Valley, and Marlborough ranges, and 10 am Thursday for Nelson Lakes. The rain is then forecast to move to the northern and western regions of the North Island from Thursday into Friday.

Makgabutlane said it was difficult to predict exactly how much rain would fall. Initially, the heavy rain is forecast for the west and top of the South Island, including Nelson, Tasman, parts of Marlborough, Buller, and down the West Coast.