The rain is expected to start falling in Northland from 3pm.
A heavy rain and strong wind watch is in place for Auckland from 9pm and lasting 12 hours, with rain, gales and thunderstorms set to pummel the storm-ravaged region.
Niwa warned Auckland would experience the worst of the incoming storm either side of midnight.
Northland would have a rough first half of the night and Waikato and Bay of Plenty would be lashed by the storm from midnight to dawn.
Very sodden grounds from a wet last few months means it won’t take high rainfall accumulations for impacts to be felt across parts of New Zealand, MetService said.
Surface flooding, landslips and rapidly rising streams and rivers were possible for areas under heavy rain warnings and watches.
The incoming system was expected to move through quicker than last week’s deluge but high rainfall intensities were still possible, the forecaster warned.
Niwa said the bad weather will be spawned from moisture in the tropics and is expected to affect northern areas before becoming more widespread across the weekend.
A number of heavy rain warnings were also in place for regions across the South Island including Tasman west of Motueka, Westland from around Otira southwards to Bruce Bay and Eastern Otago between Oamaru and Clutha River.
MetService Meteorologist Peter Little said a low-pressure system was expected to track across the central North Island on Saturday, bringing another round of rain or showers to most regions, along with a period of westerly gales and large wave conditions to northern regions.
“The gusty westerly winds and already sodden soil, means people are advised to be prepared for power outages due to falling trees disrupting power lines,” Little said.
The west of the North Island and Tasman region are likely to be the wettest places, Little said.
Yesterday Niwa warned the storm could be damaging.
The forecaster reported that the odds for wind gusts exceeding 70km/h is high for much of the North Island on Friday and Saturday. Some areas could also get wind gusts of more than 100km/h.
Between 50mm and 100mm of rain is possible for parts of the island by midnight Friday.
MetService said the bands of rain will be fast-moving, and it expects large waves along exposed coastlines.
Up to 150mm is likely about the ranges of the South Island.
