A tropical low is set to batter the North Island with heavy rain and gales until Easter, a forecaster says.

Weatherwatch.co.nz said storms hitting Fiji would start setting in over New Zealand this afternoon.

Head weather analyst Philip Duncan said "relentless" gale force winds would affect Waikato, East Coast, Gisborne and Hawke's Bay for six days.

Heavy rain could cut off towns in already-sodden areas of East Cape, while coastal communities could be affected by massive swells, he said.

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"This storm system is literally stretching from here to Fiji... it's just going to be relentless for the next six days.

"There's a high risk for landslides and a high risk of flooding. Communities could be isolated again. There's going to be this relentless wind that will be gale force."

A large high to the south was holding the storm system in place over the North Island, Mr Duncan said.

He said large centres including Auckland and Wellington could expect to see heavy rain, mixed with patches of blue sky, throughout the week and into Easter Weekend.

However, the east coast of the North Island and exposed areas of Waikato would be hardest hit, he said.

Metservice said heavy rain could be enough to cause slips and surface flooding, as well as hazardous driving conditions, in some areas this week.

It said rainfall could be intense over Gisborne and Hawke's Bay on Wednesday and Thursday.

There was a risk that severe gale force winds may develop in parts of Taranaki, Taupo and eastern Bay of Plenty, it said.

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