There was "threat to life from dangerous river conditions, significant flooding and slips" as a deepening low-pressure system east of the North Island brought heavy rain and severe gales to several regions, the weather bureau said on Sunday.
The worst weather was forecast to hit late on Sunday, followed by a slow easing of conditions on Monday, it said on its website, after heavy rain began battering large swaths of the country on Friday, sparking the floods.
Authorities on Sunday had a state of emergency in place for the districts of Waipa and Otorohanga, an agricultural region 180km south of the country's most populous city, Auckland, and home to about 10,000 people.
The Otorohanga District Council said on Facebook geotechnical teams "spent the night assessing slips and checking the structural stability of roads" in the area.
Some 4291 properties remained without power on the North Island, energy company Powerco said on its website.
A man died in his car in floodwaters on Saturday, authorities said, adding about 80 people were evacuated to an emergency centre.
Images shared on social media showed vast semirural neighbourhoods submerged and collapsed sections of road where floodwaters had receded.
Six people were killed in January after heavy rains triggered a landslide at Mount Maunganui on the North Island's east coast, bringing down soil and rubble on a site crowded with families on summer holidays.
