States of local emergency have been declared for Ōhura in the Ruapheu District and the Whanganui District due to heavy rain.
Eighteen people have been evacuated from small town in the central North Island.
The district council declared a State of Local Emergency at 3.21am today after 100mm of rain had fallen within 24 hours.
An Emergency Operations Centre has been activated at the council's main office in Taumarunui where the council will coordinate the response and support affected residents.
The Minister for Emergency Management and Recovery, Mark Mitchell, will travel to Taumarunui today give a first-hand update on the weather.
Mayor Weston Kirton told RNZ the Minister has allowed the council to use an Air Force helicopter or fixed-wing aircraft to help people stranded in Ōhura. Red Cross was also available to provide food and other resources, such as bedding.
Mitchell was expected to fly in by helicopter from the Air Force's largest base in Ohakea to Taumaranui, and then would head to Ōhura with Kirton.
The town was completely isolated, with a mixture of residents and tourists stranded. Those who have been evacuated are in the Ōhura Memorial Hall, in Ngarimu St, being looked after by "some of the local people with a limited resource".
Resident Mike Crowley returned home on Saturday afternoon, which was "a pretty rough trip home coming up from Whangamōmona on the Forgotten World Highway", but did not expect the inundation of water.
He said another resident, who had been living in Ōhura for 35 years, warned him that it was going to flood about 11pm.
There had been a similar flood in 1998 and 1956.
"A lot of the houses that were affected then, the ones that are still lived in, have been affected again. So there's some people that are going to be quite devastated."
Crowley believed they were unable to be insured due to the risk. Six people had chosen to evacuate, but Crowley had remained at home.
"I'm in the flood area, but I built my little whare, you know, a metre above ground, and 500 above the '98 flood. So yeah, I'm pretty safe."
Crowley had driven around the town and did a Facebook Live from Ngarimu St earlier on Saturday.
"It was completely covered at 3am this morning. It's probably dropped three feet.
"It didn't go into the old BNZ house on the main street, but it was right up to the doorway. Whether it got in the Cosmopolitan Club, I'm not too sure yet. I don't think anyone's been in there for a look. The old Ford dealership - that's got water flowing through it, that old building."
Crowley said it was "nothing the town hasn't dealt with before", but thought people would think twice about living in Ōhura in the future.
"You've got to be a little bit hardy, I guess, to live here, but it's a great little community that support[s] each other. Everyone bands together and there's never much trouble in this town, if any, you know. It's just, yeah, [a] really great community."
Meanwhile, an emergency mobile alert was sent to the people in Whanganui area, Civil Defence advised this morning.
Heavy rain in the upper reaches of the Whanganui River, combined with high tide, was forecast to bring possible flooding to Anzac Parade and Taupo Quay areas, and to the Putiki suburb about 1pm today.
People should prepare to evacuate immediately and Civil Defence staff were door knocking in these areas. If you feel unsafe, leave immediately.
In Bay of Plenty, a tornado has reportedly cut power to 75 homes in Tauranga's Welcome Bay, according to Powerco, and a total 276 properties still without power across its network.
State Highway 3 between Mokau and Piopio in northern Taranaki will remain closed today following more heavy rain and slips overnight, the New Zealand Transport Agency advised.
The stretch of SH3 closed overnight pending a safety assessment this morning.
"Crews are continuing to assess SH3 with trucks and excavators currently working to clear lanes."
Within the first kilometre of the gorge, 25 truckloads of material had so far been removed from the road, with more to come, it said.
SH43, the Forgotten World Highway between Taumarunui and Whangamōmona, was now open under traffic management and reduced speed.
