Battered by rain since Friday, Auckland, New Zealand's largest city of 1.6 million people, remained under a state of emergency on Sunday.
The nation's weather forecaster, MetService, warned of more severe weather on Sunday and Monday for the north island.
Intense rainfall could also cause surface and flash flooding, it said.
The focus of the emergency has moved south, with Waitomo District - about 220 kilometres from Auckland - declaring a state of emergency late on Saturday.
Police confirmed a man missing after being swept away on Friday in Onewhero, a rural village about 70km south of Auckland, had died.
"The most horrific part of it is that we've lost lives," Deputy Prime Minister Carmel Sepuloni told reporters in Auckland.
On Sunday, police said they were assisting with traffic management and road closures after heavy rainfall "caused numerous slips, flooding and damage to roads".
In nearby Bay of Plenty there was also "widespread flooding", police said, as well as a landslide that had knocked down a house and was threatening neighbouring properties.
"Police are asking those in areas experiencing severe weather to ... not attempt to travel on the roads, many of which are currently undriveable," police said.
Thousands of properties remained without power, while hundreds were without water, authorities said on Sunday.
Air New Zealand said the airline's international flights in and out of Auckland would resume from noon on Sunday (2300 GMT on Saturday).
On Saturday, Prime Minister Chris Hipkins, less than a week in office, flew by helicopter over Auckland before touring flood-hit homes.
He described the flood impact in the city as "unprecedented" in recent memory.
More than 2000 calls for assistance and 70 evacuations were recorded around Auckland - the nation's largest city - due to the inundation, the New Zealand Herald reported on Saturday.
