A large low makes landfall in the North Island on Wednesday, bringing heavy rainfall and strong gales to the northernmost parts of the country.
The low, which is currently building in the Tasman Sea, begins moving towards New Zealand on Tuesday before striking Northland later on Wednesday.
MetService has now issued a heavy rain warning for the Far North and a heavy rain watch for the Auckland region and the Coromandel as "a low pressure system drags down significant moisture from the north".
"The Orange Heavy Rain Warning kicks off from 11am on Wednesday and drifts southward into Thursday with a small possibility of localised downpours," a post on the forecaster's Facebook page reads.
"The rainband is associated with some gale northeasterlies and the greatest risk for damaging winds is through the Auckland region from late on Wednesday."
Weather Watch warns the rainfall totals for parts of the upper North Island "are pretty large" - but they won't be widespread.
"It's over 100mm of rain between now and next Tuesday. This low pressure system that will slowly move in will be feeding in a sub-tropical nor'easter," weather analyst Philip Duncan explained.
"Places like Auckland are right on the edge of that... Some in the north might get to the 80-90mm mark. Further to the south, around the Hunua Ranges, where we need the rain, it may be dropping down to 50mm.
"The eastern side of Northland, most of the Coromandel and around Gisborne and East Cape - these are the areas with the highest risk of slips and isolated flooding."
On Sunday, NIWA Weather warned the low would bring "copious rainfall in the north, including Auckland" - consistent with a "La Niña-like atmospheric pattern".
"From Wednesday, a Tasman Sea low will siphon moisture from near Papua New Guinea toward northern New Zealand... It will bring heaps of moisture to northern New Zealand later this week."
NIWA says weather systems like the one arriving on Wednesday will likely be "semi-regular visitors" for the next few months.
"The seasonal outlook calls for near normal rainfall in the north of the North Island and normal or above normal rainfall in the east of the North Island. That's a trend in the right direction."
