MetService says a large high remains slow-moving to the east of New Zealand.

"Meanwhile, a low to the north of the country is forecast to move slowly southwards to lie west of the North Island on Thursday and Friday," says a MetService spokesperson.

"As the low approaches it is expected to bring strengthening east to northeast winds to northern New Zealand, and rain to much of the country but especially northern and western regions."

For Bay of Plenty, there is moderate confidence that a rainfall warning will be needed on Friday.

For Northland, there is moderate confidence that rainfall amounts and the wind strength will reach warning criteria on Wednesday, Thursday and Friday.

For Auckland, Great Barrier Island and Coromandel Peninsula, there is moderate confidence rainfall amounts will reach warning criteria on Thursday and Friday.

For Auckland, Great Barrier Island and eastern Waikato, there is moderate confidence of severe east to northeast gales in exposed places on Thursday and Friday.

For northwest Tasman, there is low confidence of heavy rain on Thursday but this increases to moderate on Friday.

For Buller and Westland from Otira northwards, there is low confidence of warnable amounts of rain on Friday, mainly about the ranges.

For Westland south of Otira and Fiordland, there is low confidence rainfall amounts will reach warning criteria on Thursday and Friday, mainly about the ranges.