The fine long weekend weather is set to come to an abrupt end with heavy rain, gales and snow expected to batter the country over the next few days.

A complex weather system is forecast to cross New Zealand overnight tomorrow, bringing gale-force winds and heavy rain to much of the North Island on Tuesday and snow to low levels in parts of the South Island on Wednesday.

MetService spokesman Daniel Corbett said a storm system would push warm air and northerlies across the North Island, and a southerly front would bring bitterly cold air across the South Island.

The engine room of the system would settle over Cook Strait on Wednesday before clearing on Thursday and Friday.

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The MetService has issued severe rain warnings for eastern Bay of Plenty, northern Gisborne, Buller and northwest Nelson, where 100mm or more of rain was expected.

Severe northerlies gusting to 140km/h are likely throughout much of the lower North Island including Gisborne, Hawke's Bay, Taranaki, Wanganui, Wellington and Wairarapa.

In Auckland, heavy rain and strong winds were expected later tomorrow.

"It's wet, it's windy for the likes of Auckland, and then a little bit cooler as you get into the later parts of the week," Mr Corbett said.

The heavy rain would coincide with high king tides on Tuesday evening, with a risk of coastal flooding in Auckland, Northland, Waikato and Bay of Plenty.

In the South Island, snow to low levels was expected overnight Tuesday, with heavy falls of up to 40cm in north Canterbury and inland Marlborough likely to make road travel difficult on Wednesday.

WeatherWatch forecaster Howard Joseph said the heaviest rain was expected in the Bay of Plenty and the East Cape, with strong winds further south.

"There's also a chance for some pretty heavy gales, possibly approaching the severe levels, for Wellington and the whole lower part of the North Island."

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Mr Joseph said king tides were not expected to be a big problem.