Northland and the top of the South Island are most at risk of flooding as a "significant weather event" brings heavy rain and strong winds to large parts of both the North and South Island.
A trough embedded in a humid northerly air flow was driving the deluge to cap King's Birthday weekend and kick off meteorological winter.
Weather warnings held over from yesterday and, at 10am this morning, further warnings and watches expanded into the Bay of Plenty, Gisborne, Coromandel Peninsula and central North Island.
MetService said severe weather warnings and watches would remain in force through today and into Tuesday as the complex weather system tracks east across the country.
The regions facing 'risk of downpours' as weather system sweeps country - Watch on TVNZ+
MetService meteorologist Paris Marshall said a weather station in Golden Bay had recorded close to 300mm of rain in the 24 hours to 9am Monday, with more rain still expected.
"Even though the West Coast is getting the most accumulations, potentially up to 350mm, the Nelson and Buller areas do not frequently get this kind of rainfall," she said.
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Tasman District Council said the weather event would be the most significant to hit the region since the June/July 2025 floods in some areas.
"Areas of most concern for heightened impacts would be the Riuwaka River and Tākaka Hill, Upper Motueka from Motupiko down to Tapawera, and the upper Wai-iti River above Wakefield," the council said.
At the top of the North Island, around 30mm of rain fell on Kaitaia in an hour this morning.
"That is expected to spread to the rest of Northland this morning, and we might see rainfall rates like that elsewhere."
Marshall said the broad band of warm, humid air stretching across the country could bring downpours of up to 40mm an hour across parts of the upper North Island.
"For Northland and Auckland these downpours are possible overnight and if you happen to live in a flood-prone area it's worth being prepared before going to bed tonight."
Strong winds were also becoming a factor, with watches and warnings in force for Northland, Auckland, Great Barrier Island and Taranaki.
Marshall said Northland had already recorded gusts of up to 115km/h, with strong northeasterlies expected to spread south through the day.
"I do not recommend any boaties going out in this weather, especially around Colville Channel. You're just going to get blasted essentially by these northeast winds potentially approaching severe gale."
Canterbury records driest May
While the north and west are being drenched, the other side of the Southern Alps tells a starkly different story.
Canterbury has officially recorded its driest May on record - just 5.8mm of rain falling throughout the month.
The previous record was set in 2012, when 11.2mm fell.
Marshall said the Southern Alps continued to block moisture from reaching the Canterbury Plains, leaving parts of Canterbury and other regions such as Manawatū among the driest in the country during May.
While rain was expected to ease across much of the country by Tuesday evening, MetService said another band of rain could approach later in the week, potentially bringing further watches and warnings for parts of the western South Island.
Full list of weather warnings and watches
Heavy Rain Warning - Orange
Northland - 20 hours from 9am Monday to 5am Tuesday
Bay of Plenty and Rotorua (west of Whakatane) - 21 hours from 6pm Monday to 3pm Tuesday
Bay of Plenty east of Whakatane and Gisborne/Tairawhiti ranges - 21 hours from 6pm Monday to 3pm Tuesday
Tongariro National Park - 19 hours from 6pm Monday to 1pm Tuesday
Taranaki Maunga - 23 hours from 9am Monday to 8am Tuesday
Tasman District northwest of Motueka - 17 hours from 9am Monday to 2am Tuesday
Ranges of Buller - 15 hours from 9am Monday to 12am Tuesday
Richmond and Bryant Ranges (including Rai Valley) - 19 hours from 9am Monday to 4am Tuesday
Westland south of Hokitika - 13 hours from 9am Monday to 10pm Monday
Heavy Rain Watch
Coromandel Peninsula - 17 hours from 4pm Monday to 9am Tuesday
Auckland and Great Barrier Island - 6 hours from 1am Tuesday to 7am Tuesday
Waikato, Waitomo, Taumarunui and Taihape (north of Raetihi) - 10 hours from 12am Monday to 10am Tuesday
Taranaki (north of Eltham) and northern Whanganui hill country - 11 hours from 9pm Monday to 8am Tuesday
Taupo - 19 hours from 6pm Monday to 1pm Tuesday
Parts of Nelson and Tasman Districts - 18 hours from 9am Monday to 3am Tuesday
Ranges of Marlborough (Wairau to Awatere Rivers) - 19 hours from 9am Monday to 4am Tuesday
Fiordland - 20 hours from 9am Monday to 5am Tuesday
Strong Wind Watch
Auckland and Great Barrier Island - 14 hours from 4pm Monday to 6am Tuesday
Taranaki and Whanganui - 11 hours from 3pm Monday to 2am Tuesday
Taihape and Tongariro National Park - 12 hours from 6pm Monday to 6am Tuesday
Northland - 10 hours from 3pm Monday to 1am Tuesday
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