The effects of a deep low north off New Zealand will start being felt today, with much of the East Cape in line for heavy rain, while strong winds are expected in Auckland, Northland and eastern parts of the upper North Island.

Strong wind marine warnings were issued at 10.34am on Sunday for the Hauraki Gulf, Waitemata Harbour, Bay of Plenty and Hawke's Bay. And marine gale warnings for the Bay of Islands, Coromandel and Bream Head to Cape Colville.

The "weather bomb" - when a low-pressure system deepens by 24hPa in 24 hours at a latitude of 60 degrees - has already occurred, with the resulting deep low sparking a heavy rain warning from MetService for parts of the East Cape north of Gisborne.

Up to 140mm of rain is expected in the 24 hours from 10am today, according to MetService.

A heavy rain watch is also in place for Gisborne and south of the city over the same period, while a strong wind watch has also been issued for the eastern ranges of Bay of Plenty and towards the coast east of Ōpōtiki from 6am today till 3am Tuesday.

The east coast of Northland from Whangaroa to Marsden Point, as well as Great Barrier Island and the Coromandel Peninsula about and north of Whitianga were also under a strong wind watch until 6pm today.

It would be be wet across the top of the North Island, largely north of Taupō, MetService forecaster Gerard Bellam said.

"But it'll be mainly fine across the southwest and up to Waitomo."

A cold front brings wet weather to Fiordland, Southland and Otago this afternoon, moving north to South Canterbury by midnight, Bellam said.

That meant rain tomorrow and showers Tuesday, with a high - and settled weather - over the South Island by mid-week.

For the North Island, there's little change tomorrow and Tuesday, with dry conditions expected from Taranaki south to Wellington and wet weather continuing in the upper part of the island.

The north will also be windy - strong southeasterlies are expected across the top half right through till Wednesday.

Those in the Gisborne area have the bleakest weather week ahead, with rain and strong southeasterlies expected through much of the week, Bellam said.

"It's a long duration of wind and rain in that area. It's going to be quite a wet week for Gisborne."