Northland is set to be doused by heavy rain as a band of wet weather descends from the north through Auckland as it migrates south.
The downpour comes ahead of a cyclone developing around the Pacific Islands, near Fiji, which forecasters say could hit New Zealand directly.
MetService meteorologist Amy Rossiter said Northland is expecting up to 130mm of rain to accumulate tonight, mainly in the eastern hills.
Further heavy rain was expected from Friday evening to midnight.
MetService had placed a warning for the region from 6pm Thursday to 3pm Friday.
The heavy rain could cause streams and rivers to rise rapidly as well as cause surface flooding and potential slips.
The rain was a result of a humid easterly flow moving down from the north on Thursday and Friday, travelling to the upper fringes of the South Island by Saturday.
Auckland north of the city, Great Barrier Island and the Coromandel Peninsula were also under a heavy rain watch from 2am Friday to 3pm Friday.
The wet weather comes ahead of a cyclone developing around Fiji which was expected to hit New Zealand sometime next week.
It would be much bigger than Cyclone Fehi which struck the Pacific last week, Meteorological service WeatherWatch said.
MetService meteorologist Kyle Lee said MetService was aware of the cyclone forming and had a team of forecasters keeping an eye on it, but it was difficult to be precise as the cyclone was a week away.
The National Institute of Water and Atmospheric Research said today there was a moderate chance of a cyclone formation between Friday and Sunday.
They have named the system Tropical Cyclone Gita.
Cyclone Fehi's power last week saw a state of emergency declared for Dunedin and the Buller District on the South Island's West Coast.
Felled trees and slips blocked parts of State Highway 6, stranding 115 motorists near Fox Glacier.
A further 600 tourists - some with medical issues - were stranded in Haast, blocked by a 100m long 9m high slip at Douglas Bluff south of Haast.
Whangarei: Rain. E. High 25C Low 21C
Auckland: Rain. E. High 24C Low 20C
Hamilton: Rain. E. High 22C Low 18C
Tauranga: Rain. E. High 23C Low 20C
Napier: Cloud to rain. E. High 22C Low 18C
Wellington: Cloudy. High 24C Low 17C
Christchurch: Cloudy. High 23C Low 14C
Dunedin: Fine. High 20C Low 15C