A tropical atmosphere deluge is expected to hit in the coming days, with some regions bracing for serious flooding and hazardous slips.
MetService has issued heavy rain warnings for the west parts of the South Island with rainfall, in some areas, expected to reach more than half a metre in the coming days.
It has described the forecast deluge as a "significant event".
"From overnight tonight and continuing right up to Thursday evening, northern and western parts of the South Island will be pummeled by heavy rain, with accumulations expected to exceed 500mm in places! This will be a significant event."
NIWA Weather said: "This means flooding and slips are a real concern. Significant snow melt will likely contribute to flood risk."
An atmospheric river of moisture, originating from the tropics, will result in very heavy rain this week.
— NIWA Weather (@NiwaWeather) August 14, 2022
For the west of the South Island, this means flooding & slips are a real concern. Significant snow melt will likely contribute to flood risk.
Four day rainfall forecast ⬇️ pic.twitter.com/8jcNfd25kr
Weather warnings have been issued by MetService for Buller, the Tasman, Westland, the Marlborough Sounds and Mount Taranaki.
"Heavy rain may cause streams and rivers to rise rapidly. Surface flooding and slips are also possible and driving conditions may be hazardous."
In the coming days, those regions are expected to see between 400 and 650 mm, MetService said.
From overnight tonight and continuing right up to Thursday evening, northern and western parts of the South Island will be pummeled by heavy rain, with accumulations expected to exceed 500mm in places! This will be a significant event, https://t.co/qHyE5zzql5 for full details ^DM pic.twitter.com/dEr8FafsrY
— MetService (@MetService) August 14, 2022
🟧 Severe Weather Forecast 🟨
— MetService (@MetService) August 14, 2022
A persistent band of heavy rain is going to bring large accumulations of rain to the areas shown on the map.
Rain related impacts are likely and there's potential for a Red Warning.
Keep up with the latest here: https://t.co/qHyE5zhh6X pic.twitter.com/WHoaJbFJ4N
Buller's Emergency Management (BEM) has a team in place for the incoming weather, due to arrive at 3am on Tuesday.
Sandbags are being delivered to across the region, the emergency service said.
"We will work with the community coordinators in each of these locations to update where," BEM said in a post on Facebook.
In the Tasman area, MetService said: "Peak rates of 10 to 15 mm/h about the ranges on Tuesday, then 15 to 25 mm/h during Wednesday and Thursday."
At the other end of the country, in Northland, heavy rain and strong wind warnings were in place for Wednesday through to Friday.
In Auckland and most of the North Island, downpours were forecast to hold off until later in the week. From Wednesday through to Sunday "scattered rain" could be expected.