Hundreds are without power in Auckland on Friday night, a house has been left perched above a huge slip on Waiheke Island and surface flooding has hit parts of the city.
There are also reports of water coming into people's homes through basements and ceilings as the deluge continues.
WeatherWatch.co.nz issued the alert for Auckland City and region between 7.30pm and 9pm on Friday.
There is a high risk of localised surface and flash flooding and a high risk for flooding in low to medium streams and waterways.
Drivers are being warned to take extreme care and avoid driving until after 10pm. Trains have been cancelled and delayed in Auckland, mainly affecting commuters on the Eastern line.
Severe downpours have hit the North Island for the second time this week, bringing torrential rain and flooding, causing power outages, slips and road closures.
Far North Civil Defence spokesperson Bill Hutchinson said a family was reportedly trapped by floodwaters up the flood-prone Waiomio Valley, just south of Kawakawa, but emergency services were unable to reach them.
Some residents in the area had self-evacuated to Mohinui Marae.
The Kawakawa Fire Brigade was bringing in an inflatable boat in case they have to mount a rescue overnight but Hutchinson said water levels are already dropping.
Kaeo River began flooding State Highway 10 just before 6pm.
MetService has issued severe weather warnings across the top of the country as three distinct bands of rain will pass over Northland, Auckland, Coromandel, Whakatane and Gisborne in the 12 hours from 4pm on Friday.
The wild weather has stretched volunteer fire brigades with Kerikeri and Rawene particularly busy dealing with flooded homes, downed trees, blocked drains and crashes.
At the height of the storm, about 2pm on Friday, Rawene firefighters were on a roof on Clendon Esplanade trying to secure tarps to stop rain entering a home.
The weather has also taken its toll on the Far North's power network. This morning 600 households were without power, mainly in Oue, Waimamaku and Horeke in South Hokianga. Power was restored to all but 60 households by 4pm.
A Top Energy linemen had to call in police when a hostile landowner refused to allow them access to damaged lines in the Wekaweka Valley. More outages were expected overnight.
Aucklanders are also being asked to reduce their water use over the next three weeks after floods affected capacity at Ardmore Water Treatment Plant.
About half of Auckland's water comes from four water storage dams in the Hunua Ranges, where flash flooding has taken place.
