MetService says a high over the country is expected to move off to the east as a low over the Tasman Sea approaches the North Island on Tuesday.

"Rain is likely to affect western areas, but there is minimal risk of severe weather," says a MetService spokesperson.

On Wednesday, May 15, the low is likely to cross over the southern North Island during Wednesday, bringing rain to many places in the North Island and northern South Island.

"There is moderate confidence that heavy rain about eastern Bay of Plenty will require a warning, and low confidence that warning amounts of rain will fall about Mount Taranaki/Taranaki Maunga, Tasman, Nelson and western Marlborough."

The low should move away from New Zealand on Thursday, followed by a southwest flow.

"Later in the day a high may begin moving onto the North Island. About the southern South Island a strengthening northwest flow is likely.

"Heavy rain may continue to fall in eastern Bay of Plenty during the morning and there is low confidence that a rain warning will extend into Thursday.

"For southern Fiordland and Stewart Island, there is low confidence that the northwest winds will increase to warning strength by the end of the day."

A front is expected to move northwards over the South Island during Friday, bringing rain to the west and strong west to northwest winds to the south and east.

"A ridge of high pressure should lie over the North Island.

"There is moderate confidence that heavy rain in Fiordland will require a warning, with low confidence that the ranges of the Westland District will also need a rainfall warning."

The MetService says for Fiordland and Stewart Island there is low confidence that a wind warning will be needed for severe gale west to northwest winds.

"About inland areas of mainland Southland, Otago and Canterbury there is also low confidence that northwest winds will reach warning strength."