MetService is warning that heavy rain and gales could hit parts of the North Island on Monday and Tuesday.
An intensifying low-pressure system is approaching from the northwest.
"Northland will be the first to feel the brunt of this weather system with rain and strong easterly winds setting in Monday morning," MetService meteorologist Stephen Glassey said.
"The rain and strong winds will then gradually spread south over the rest of the North Island and Marlborough during the remainder of Monday and Tuesday."
The worst downpours are expected on Coromandel Peninsula, in Northland and in northern Auckland.
MetService has issued a heavy rain warning for Coromandel Peninsula from 8pm on Monday to 5pm on Tuesday.
Northland and Auckland north of Whangaparaoa are under a heavy rain watch from 3pm on Monday.
Heavy rain may hit Gisborne and Hawke's Bay on Tuesday.
"Because this system is coming from the north, it contains more moisture and potential for heavy rain than your average low-pressure system," Mr Glassey said.
Easterly winds are expected to lash many areas on Monday afternoon and Tuesday morning.
Strong wind warnings have been issued for Auckland, Great Barrier Island, Coromandel Peninsula, Waikato and western Bay of Plenty. Winds could reach severe gale intensity in exposed places in these regions, while Northland is under a strong wind watch.
The low is expected to move away to the east of New Zealand on Wednesday, with rain clearing in most places and winds easing.
Another low pressure system could affect the country later next week.