Heavy rain overnight caused severe surface flooding in the Gisborne suburb of Mangapapa, forcing some families to leave their homes.
Tairāwhiti Civil Defence says heavy rain caused drains to flood and creeks to rise to about 2m, causing severe surface flooding across the suburb.
Police have been going door-to-door checking on people.
Fire and Emergency has closed roads in and around the areas from Lytton High School to Winter Street.
Gisborne mayor Rehette Stoltz said severe downpours started at 3am, and three hours later it was still "absolutely pouring".
"The rain woke everyone up in Gisborne," Stoltz told Morning Report.
"It's rain I have not heard in my 22 years in Gisborne."
MetService has extended its orange heavy rain warning for Gisborne City to 1pm.
Stoltz said city creeks were overflowing and flooding people's homes.
The Matokitoki Stream which ran through several neighbourhoods had received so much rain it was causing flooding in the city, in areas not hit by Cyclone Gabrielle, she said.
Gisborne Civil Defence said 15 households were evacuated overnight.
The latest deluge, following Cyclone Gabrielle, was likely to have caused damage to properties and stormwater inundation, Gisborne District Council chief executive and Civil Defence spokesperson Nedine Thatcher Swann said.
"We just haven't had a break in this weather to get in and remediate everything.
"The ground is saturated, we're watching our rivers, and the our creeks are behaving in different way.
"It's pretty big for us here."
Overnight about 40mm of rain fell over two hours, she said. It was a surprise that flooding was concentrated in Mangapapa, which had not been affected by flooding in recent years.
"I guess this is part and parcel of what we'd be expecting as our climate changes. We're seeing rain fall in concentrated areas and in different parts."
Resident Kory Moorcock who evacuated his family overnight said it looked as if a tornado had ripped through his property.
There were trees, fences and bridges down with silt strewn through his section.
Moorcock who is a builder evacuated his family from their Shelley Road home just after 3.30am before finding a flooded bridge.
He said they were left temporarily stranded before floodwaters began to subside.
Riverdale resident Sarah Adams said the creek behind her home turned into a nearly 30m expanse of water early this morning.
She said the flooding had partially subsided by sunrise but she was watching in trepidation as the waters rose.
It was difficult to see her neighbourhood suffer a repeat of the flooding.
"It's quite hard for my son - he's only three and thinks every time it's going to rain we'll flood and unfortunately it's proving to be like that."
She has taken the day off to look after her child and check on friends in nearby Valley Road.
More rain fell overnight in Hawke's Bay with reports of flooding in some areas.
MetService has issued an orange heavy rain warning for the Hawke's Bay district of Waiora district to 2pm.
Heavy rain caused further extensive damage to State Highway 5 connecting Napier to Taupō.
A section of the highway at Te Pōhue and Glengarry has slipped away and washed out all the lanes.
Only one lane was blocked previously.
Civil Defence issued an update saying the road was completely impassible an an assessment would take place when it was safe to do so.
The section that slipped away is about 30m in length and is near the effluent ponds at Glengarry Hill.
Napier Mayor Kirsten Wise urged people to avoid driving through flood waters.
She told Morning Report updates on affected areas in the region were still coming through.
"We're particularly encouraging people to avoid driving between Napier and Hastings if possible," she said.
"There is still some surface flooding here in Napier, mainly around Awatoto area and I have been contacted by a resident in Waiohiki, which actually sits within Hastings but right on the boundary.
"They were a little concerned after the rain in the night, so I will be following up about that community this morning."
A evacuation centre in Wairoa has been reopened.
Wairoa District Council said the majority of the flooding after heavy rain was in the township and the areas north or Wairoa River.
It said the ground was already saturated and silt was blocking drains and stopping the water from running away.
Hawke's Bay Civil Defence said Memorial Hall can take those who need to escape floodwaters.
Two people have been moved from their home in Freyberg by emergency services after a stop bank failed on a stream.
MetService said 97mm of rain had fallen so far today in Wairoa, with 20mm of that between 5 and 6am.
Wairoa's deputy mayor Denise Eaglesome-Karekare told Midday Report the north side of Wairoa had flooded in parts because the drains and culverts were full of silt.
She said approximately 50 more properties had flooded from the rain, on top of the hundreds that had already been damaged.
"People who rang me said that actually more rain fell last night, then Cyclone Gabrielle," she said.
The recovery had been set back weeks and had made the housing shortage worse, she added.
Prime Minister Chris Hipkins is visiting the town tomorrow.
She said she'd be pushing for urgent government support.
"Our message to him will be that we need to get our community back to as normal as we possibly can.
"So we need all the resources and support that government has. We need our share of the $250 million that Grant Robertson has been given.
"We need State Highway 2 rerouted. We need to be able to get to Napier, Hawke's Bay. That's where our health services is."
Unison struggles to reinstate power infrastructure
Several communities in the region remain without power.
Unison representatives will meet with people in Puketapu today, and Tangoio and Tutira tomorrow, to discuss the situation.
Incident controller at Unison Jason Larkin told Morning Report networks destroyed would be replaced, but infrastructure washed away by river flooding would probably need to be build differently.
Larkin said there were currently 2700 customers without power, with about 2500 of those being in rural areas. A large generator was being used to supply a limited amount of customers, while crews worked on restoring lines.
"We've got crews out there working around the clock ... and we're looking at all available options," he said.
"There are areas where the network has just been really washed away by these these torrents of water and logs, and it's going to take some time to rebuild the supply to areas like Patoka. We're looking at options like local generation and we're now generating at a number of sites. North Puketapu is one area."
The generator brought into the area last week was started up by crews who managed to access the area last night.
"Our challenge going forward with that site is ongoing fuel supply," Larkin said. "But we're working on that with Emergency Management, with council and regional council, and hope to have a solution to see fuel flying into that area from this afternoon."
At full load the generator will give power to about 400 customers, using about 4000 litres of fuel a day.
The reinstatement of a temporary crossing at Rissington would allow tanker access to bring fuel in with two 2000 litre loads per day, Larkin said. Safe storage at Patoka was also being looked at.
"There are areas where it's going to take weeks, if not months, to repair and rebuild the network," he said.
The company was assessing the needs of communities, and knew some communities were more resilient than others, he added.
But bebuilding destroyed infrastructure would be a unique challenge.
"The flooding lower down in the rivers has been a bit of a game changer. It took out the main connection to the national grid at Redcliffe, but also took out some of our key supply lines out to these rural areas. We will be rebuilding those," he said. "We will probably have to do it differently...
"Even rerouting them down the side of the road at the moment there is about 3m high piles of silt on the side of the road because that's what's been needed to clear those roads for access."