Fans leave Mt Smart Stadium, where about 40,000 people were expected to attend an Elton John concert; a car drives through flood water at Auckland Airport on Friday. AP / Reuters

About 40,000 people were expected to attend the evening concert at Mt Smart Stadium in New Zealand's largest city. Thousands were already at the venue when organisers decided to cancel not long before John was due to take the stage at 7:30pm. The concert was billed as a final farewell tour for John.

Frontier Touring, one of the concert promoters, tweeted the concert had been cancelled due to unsafe weather conditions.

Many concertgoers who had braved the conditions were frustrated the decision hadn't been made hours earlier.

Auckland mayor Wayne Brown told a news conference late on Friday he was "deeply saddened" after a body was found in a northern suburb. Police have not confirmed whether the death was a result of the flooding.

Flash floods turned many of Auckland's roads into rivers as the wild weather closed the city's airport, leaving some terminals ankle-deep in water.

Auckland airport, New Zealand's largest, confirmed there would be no domestic or international departures or arrivals before noon local time on Saturday.

New Prime Minister Chris Hipkins, who was sworn in Wednesday after Jacinda Ardern's shock resignation, wrote on Twitter that government agencies were "working flat out" to help.

He said the national crisis management centre, housed under the parliament building in the capital Wellington, was helping coordinate the emergency response.

Emergency services were swamped by calls for help as civil defence officials warned residents to stay home.

Fire and Emergency New Zealand said it had taken over 1,000 calls for help, but that many calls were from people who had flooded properties. The agency was urging callers to clear the lines for those in immediate danger.

Police also urged people to only contact emergency services if they were in "life-threatening" danger.

Brown said he would visit the worst-affected communities on Saturday to assess the damage and disruption as the clean-up begins.

"It'll be a major, major job," he said.

Video posted online showed waist-deep water in some places, and authorities were asking residents in flood-prone areas to be prepared in case they needed to evacuate.

Lawmaker Ricardo Menéndez posted a video of water surging into residential houses.

"We’ve just had to evacuate our home as the water was already rising rapidly and coming in aggressively,” he tweeted.

Agencies