Emergency services are warning people to stay away from Auckland's northern beaches where homes are threatened as high tide peaks and ex-Cyclone Lusi causes havoc.

Lusi hit Northland on Friday night, unleashing 91mm of rain near Whangarei over 27 hours and wind gusts of 139km/h at Cape Reinga.

A storm surge damaged a restaurant on Paihia's wharf and a seawall, several boats came ashore, Marsden Point was closed to all shipping and roofing iron lifted on a building in Mangawhai.

On Saturday, Auckland became the target.

Localised power outages, surface flooding and landslips occurred across New Zealand's largest city. Three boats broke from moorings and ferry services were disrupted.

One ship heading to Ports of Auckland was diverted to shelter off the Coromandel Peninsula.

Auckland Council Civil Defence controller Clive Manley says weather conditions will deteriorate and coastal erosion will be a problem from 4pm to 10pm on Saturday at Snells Beach, Waiwera, Orewa, Milford, Cheltenham and Whangateau.

High tide is expected at 8pm.

"It's best to keep away from beaches," he said.

Civil Defence is preparing to evacuate as many as 50 houses in Milford, Cheltenham, Orewa, Whangateau, and Wairewa, Radio New Zealand reports.

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Lusi batters Auckland beaches