MetService says there have been some heavy rainfalls recorded overnight in Northland as a belt of wet and windy weather moves across the upper North Island.
It said 10mm of rain was recorded in Kaikohe between 2am and 3am, and again between 4am and 5am.
Northland and Coromandel are both under orange heavy rain warnings, with MetService warning the expected downpours could cause rivers and streams to rise rapidly and make driving conditions hazardous.
A heavy rain watch is also in place for Auckland and strong wind watches are in force for Northland, north Auckland, Great Barrier Island and Coromandel.
There is also a strong winds warning in place for the Auckland Harbour Bridge and Waka Kotahi is urging motorists to take care.
Thames Coromandel District Council said people needed to heed the warnings that up to 200mm of rain could fall across the entire district, with gale force easterly winds reaching up to 100 kilometres an hour.
Civil Defence Controller Garry Towler said people should prepare and make plans in case there were slips, falling trees, flooding, road closures or power cuts - as the bad weather could last up to a week.
Vector said it had been monitoring the electricity network overnight, as heavy rain and high winds began sweeping into Auckland in the early hours.
The lines company said suburbs that had overhead powerlines were at most risk from the latest bout of bad weather.
Chief Operations Officer Peter Ryan said crews had been on standby overnight and Vector was monitoring the state of the network 24/7.
"We'll be dispatching crews into the field whenever we get significant loss of outage, safety being paramount - some of the work we do can really only safely be conducted during daylight hours."