Northland can expect 60-90mm of rain on top of what has already fallen, with peak intensities of 20 to 30mm per hour, especially in possible thunderstorms this afternoon and evening.
Heavy rain may cause streams and rivers to rise rapidly. Surface flooding and slips are also possible and driving conditions may be hazardous, MetService warns.
Thunderstorms are also possible in Auckland this afternoon and evening.
Other parts of the country won't stay dry either, MetService meteorologist Stephen Glassey says.
The low-pressure system bringing rain just now will hang around over the top part of the North Island into next week, Glassey says.
It'll remain unsettled across New Zealand for the next few days until late Monday/Tuesday when a ridge of high pressure will start to move in.
Some cold southerly winds might blast through early next week but there's "nothing too unusual about that", Glassey says. "It's still winter."
New Zealand's main centres today and tomorrow
Auckland today: 18C. Tomorrow: 17C
Tauranga today: 19C. Tomorrow: 18C
Wellington today: 13C. Tomorrow: 13C
Christchurch today: 11C. Tomorrow: 12C
Dunedin today: 9C. Tomorrow: 10C
- MetService