There is "absolute chaos" in parts of West Auckland in this morning as wild weather causes extensive flooding.
People in flood-prone areas should be ready to leave, overriding level 4 requirements to stay at home, Auckland Civil Defence says.
There are reports of flooding in Henderson, Waitakere, Ranui, Kumeu, Piha and Bethells Beach overnight.
Firefighters had to resort to using jetskis to rescue trapped motorists as the water kept rising.
Residents are being evacuated, houses have been flooded and cars swept away. A witness said this morning it was "absolute chaos" in Kumeu, with all roads in and out blocked by flooding.
"There's one car parked with water up to its windows. There's a stream running off the buildings and footpaths, cars are floating around," he said.
"I've never seen anything like this."
Civil Defence has been monitoring the heavy rain and wind since midnight and is warning this morning more people may need to evacuate. A heavy rain watch is in place until 1pm today.
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The rain band is expanding into the northwest this morning.
"Remember, do not attempt to drive through floodwaters. If your life or property is at risk, dial 111."
More than 150 calls about flooding have come in to the fire service overnight - the majority from West Auckland.
A witness told the Herald numerous homes were flooded in and around Birdwood Rd in Swanson and cars were being swept down the road.
"Houses are underwater, cars are flooded and kids are being plucked from their homes in their pyjamas."
The witness said emergency services were out trying to help people and it's understood at least one home was at risk of collapsing.
He saw one man carrying two children through shoulder-height flood water.
Another man and his wife were fleeing with one bag of belongings, all they had time to grab as the water rose through their home.
"It is just absolutely teeming down, the rain is just driving so hard."
"It's still an emerging situation," Auckland's Civil Defence deputy controller Rachel Kelleher said this morning.
Auckland Civil Defence Emergency Management had been monitoring the heavy rain and wind conditions since just after midnight.
In a statement, Fire and Emergency said it is continuing to respond to calls about flooding around Auckland.
"Between 9.30pm and 4am, we received more than 150 calls for assistance.
"Most of the calls related to flooding into residential properties. We were also called to help people stuck in vehicles.
"We were called to incidents right across Auckland and the North Shore, with the bulk being in West Auckland, and up to Kumeu."
Henderson volunteer firefighters overnight said they were busy dealing with multiple calls to flooding, trees and powerlines that had come down and people trapped by floodwaters.
Residents in and around Kumeu have also reporting flooded roads, backyards and streams that have breached their banks while a family in Whenuapai said the gusts were so strong their trampoline was blown over.
Henderson resident Peter Lee told the Herald he woke up around 12.30am to the sound of his toilet bubbling.
"I thought what the heck is that?"
"I looked out and it [water] was high so I woke up the wife and kids and thought we better get ready to go."
In the time the family was getting to leave their property Lee said the water had risen one meter - and was "crotch deep".
"It was probably 40 centimetres up the walls inside the house," he said.
Lee and his wife also own a cattery and were able to safely evacuate all four cats currently staying there.
They left their flooded home in the early hours of the morning.
"We managed to get the car out but it was sitting in quite a bit of water," he said.
"Basically everything is damaged."
"It's just a big muddy sludge under the carpet," he said.
A Huapai resident said her garage, where she had her office, had flooded twice already in the night.
While there wasn't too much damage the carpet was soaked and there were commercial drying machines in there now. The house, which is on higher ground had however escaped the flooding.
"This area is getting hit hard tonight," she said.
Michelle Cawley noticed her backyard had started to flood when her little dog decided to go outside at around 10.30pm.
"I let him outside the ranch slider and he was crying and crying on the deck so I went out there to see what his problem was and I was just like oh my lord."
"I can't even explain it, my family have been here 18 years and this has never happened."
The Taupaki resident said the water was "at least waist high".
Waitakere Volunteer firefighters asked residents to stay at home saying "Please DON'T driver! Much of the Township is flooded."
Henderson Massey local board member Will Flavell advised West Auckland residents to stay off the roads and keep pets and children away from the water.
He told the Herald he had spoken with Auckland Transport in the early hours of the morning about getting help for those who need it.
"Auckland Transport have assured me they will get contractors out to Ranui [and] Henderson as quickly as they can."
Flavell said he has also has spoken with some people in the affected suburbs who said firefighters were there and evaluating some properties.
He had also witnessed flooding himself.
"I've seen flooding in different homes and in different streams and creeks."
MetService meteorologist Daniel Corrigan said some parts of West Auckland had recorded close to 90mm of rain in the 12 hours to 1am.
Some areas in Auckland had also recorded 20mm-30mm of rain in an hour.
And, the rain wasn't expected to stop overnight.
"We are expecting to see more rain for most of the day."
The flooding comes after the Auckland region saw about 400 lightning strikes over a roughly three-hour period Monday evening - putting on a light show for two days in a row.
While some areas are more prone to thunder and lightning than others, it's unusual anywhere in New Zealand to see lightning and thunder two days in a row, said MetService forecaster Allister Gorman.
"We usually share them around more," he said.
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Most of the Auckland thunderstorms on Monday were around Helensville and Kaipara Harbour.
"The Auckland area is under a moderate risk of thunder storms until tomorrow morning," but it's unlikely to compare to last night's spectacular show," Gorman said.
The region remains under a heavy rain watch due to a slow-moving front, meaning people should be wary while travelling or if in flood-prone areas. While not all areas will be hit by heavy rain, it remains a possibility.
"There is some uncertainty as to exactly where the heaviest rain will fall, but rainfall amounts may approach warning criteria in the vicinity of this rain-band," MetService has warned on its website.
The thunderstorms are expected to move north towards Cape Reinga on Tuesday, possibly leaving New Zealand by Wednesday, Gorman said.
Motorists are being warned to expect hazardous driving conditions.