Busy tourist routes could be closed for up to three months after parts of the country were pounded yesterday with the heaviest rainfall in 40 years.

Landslips made roads in and out of Golden Bay impassable. Nelson's major arterial route, and more than 40 homes in Cable Bay, would be cut off for more than a week, Civil Defence's Jim Frater said.

A Civil Emergency was declared on Wednesday night and Frater estimated the repair bill to reach millions of dollars.

Yesterday, helicopters dropped food and essential supplies into the worst hit areas.

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Many people were without power and running water, including a six-months pregnant Australian tourist and her husband, who were airlifted to safety yesterday afternoon. Sydneysider Kim Knight, 33, said she had never experienced scarier weather.

"Through the night, we heard all the thunderous slips happening through the valley. The rumbles of rocks and earth and trees slipping down made quite a roar," she said.

The couple planned to finish their holiday in Wellington and fly home on Tuesday.

Taranaki was also hit with heavy downpours. A severe weather warning was lifted at 2pm yesterday but a severe watch remained for Waikato, Coromandel and most of the central North Island. MetService had predicted 50 to 70mm of rainfall over a 6- to 8-hour period.

Two cabins at Oakura Beach Holiday Park, near New Plymouth, were damaged when a cliff face slipped into the park. A Nelson family abandoned their tent and went home. No one was injured.