The incoming deluge could lead to flooding and slips in areas saturated by midweek rain.
Northland, Coromandel Peninsula, Mt Taranaki, Bay of Plenty, Rotorua, the ranges of Gisborne north of Ruatoria, Tasman west of Motueka, Buller and Westland are under heavy rain warnings and watches.
MetService has also added a strong wind watch for South Taranaki, inland Whanganui and Taihape tomorrow and a heavy snow warning for the Canterbury high country.
A number of South Island alpine passes are under road snow warnings with the forecaster warning of "impactful snow" across inland regions.
"With the upcoming school holidays it could be worth taking the weather into account for your travel plans," warned MetService.
It's the first several major storms that forecasters say will sweep across the country in the next fortnight.
In its severe weather outlook, MetService says as well as heavy rain approaching warning criteria, Northland would likely be rattled by thunderstorms.
The large low and associated fronts were expected to move onto New Zealand from the west tomorrow, bringing heavy rain to many areas and strong winds to the north and snow to the central South Island.
Niwa weather said a series of strong lows, fuelled by rain from the tropics, were expected over the next two weeks.
Another was set to hit on Monday and more later in the first week of the holidays.
"The theme will be wetter than normal conditions with the potential for flooding," said the forecaster.
Weatherwatch.co.nz said the North Island would bear the brunt of the most unsettled weather in half a decade, with at least six lows bringing bursts of rain and wind in the next 10 days.
The forecaster said although not all lows were stormy, at least three were expected to produce "severe weather risks".
This winter pattern was the most unsettled the North Island had seen in half a decade, after five years of general rain shortage across the top half of the island, said the forecaster.
