Auckland night flooding brings evacuations

Frightened Aucklanders have been forced to evacuate their homes in the dead of night due to flash flooding.

A mammoth and unexpected deluge forced evacuations in suburbs of west Auckland and nearby towns, such as Kumeu and Piha.

Emergency services received 150 calls for assistance through the night.

The NZ Herald reports at least 50 homes across the region were evacuated, with flood waters yet to subside as rain continues.

"We've been dealing with drought conditions and suddenly we've got this," shocked Auckland Mayor Phil Goff told Radio NZ.

"The rain through the night was hitting around 90mm an hour which is a hell of a lot of rain.

"That's now come back but it's still around 40mm an houe. We imagine later this morning things will be getting better."

NZ weather forecasting agency MetService issued a yellow 'heavy rain watch' on Monday, upgrading it to an orange warning on Tuesday morning - only after the bulk of the rain had fallen.

"We knew it was going to rain overnight ... but there was no early indication that this was likely to cause the level of flooding it has," Mr Goff said.

"Our forecasters are pretty good but they're not miracle workers. They can't be expected to know everything. This has hit in a pretty localised way."

The fruit-growing centre of Kumeu has been devastated after 201mm of rain on Monday night - its second-wettest day since records began in 1943.

Main road shops are under a murky brown water, with many local houses and cars damaged.

Auckland remains at in a severe lockdown due to a COVID-19 outbreak, with almost 500 cases identified in NZ's biggest city over the last fortnight.

The stay-at-home orders are trumped by emergency management controls, meaning affected Kiwis can take the necessary action to safeguard property and family.

"People need to know that while we are under alert level four ... that is superseded by the more urgent requirement to get out of homes that are no longer habitable," Mr Goff said.

Emergency shelters have been set up in Henderson and Kumeu, and at least one vaccination centre was unable to open on Tuesday morning.

A silver lining is the top-up to under-pressure dam levels.

Kiwi news outlet Stuff reports Auckland's dams - historically around 90 per cent full in August - were 65 per cent full on Monday, but are sitting at 72 per cent.