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.
MetService meteorologist Paris Marshall said Golden Bay had recorded 278mm of rain in the last 24 hours.
"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."
Strong wind was also becoming a factor, with watches now in force for Northland, Auckland, Great Barrier Island and Taranaki.
"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.
"It's quite a significant drop," Marshall said.
"The rain is just not getting over the Southern Alps and leaving Canterbury quite dry."
Full list of weather warnings and watches
Heavy Rain Warning - Orange
Northland - 18 hours from 12pm Monday to 6am Tuesday
Taranaki Maunga - 33 hours from 12am Sunday to 9am Tuesday
Richmond and Bryant Ranges (including Rai Valley) - 32 hours from 8pm Sunday to 4am Tuesday
Westland south of Hokitika - 26 hours from 8pm Sunday to 10pm Monday
Tasman District northwest of Motueka - 30 hours from 8pm Sunday to 2am Tuesday
Ranges of Buller - 28 hours from 8pm Sunday to 12am Tuesday
Heavy Rain Watch
Coromandel Peninsula - 18 hours from 3pm Monday to 9am Tuesday
Bay of Plenty and Rotorua - 21 hours from 6pm Monday to 3pm Tuesday
Taupō - 18 hours from 9pm Monday to 3pm Tuesday
Tongariro National Park - 21 hours from 6pm Monday to 3pm Tuesday
Parts of Nelson and Tasman Districts not already covered - 32 hours from 8pm Sunday to 4am Tuesday
Ranges of Marlborough (Wairau to Awatere Rivers) - 22 hours from 6am Monday to 4am Tuesday
Fiordland north of Charles Sound - 27 hours from 12am Sunday to 3am Tuesday
Strong Wind Watch
Northland - 13 hours from 3pm Monday to 4am Tuesday
Auckland and Great Barrier Island - 14 hours from 4pm Monday to 6am Tuesday
Taranaki - 12 hours from 3pm Monday to 3am Tuesday
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