Evacuations are continuing into the night in Whanganui, Rangitikei and Taranaki with a state of emergency declared.
In Whanganui, about 75 people are sheltering at an emergency centre on Guyton street - and Rangitikei civil defence teams are evacuating up to 140-households in Koitiata.
The Whanganui River is expected to peak at about 9 metres at 1am on Sunday and authorities fear it may breach stopbanks in the east of the city.
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The Whanganui-Manawatu district council said rural fire crews were working with the army to get four unimogs up from Linton to help evacuate people as necessary.
We have just declared a Civil Defence Emergency there will be some people asked to leave their homes,if you are asked , please do that ASAP.— Mayor Annette Main (@MayorAnnette) June 20, 2015
Whanganui Mayor Annette Main said a Civil Defence Emergency was declared at about 4pm when it became clear the city faced a significant flooding risk during the night.
"We've got very high levels in the Whanganui River predicted to come in in the middle of the night and so we wanted to get places evacuated before it was dark," Ms Main said.
"So what declaring the emergency does for us is it enables us to do that and make the people leave for their own safety.
"You often find people don't want to leave and they've seen a flood before and they think, well it was alright last time, but this is predicted to be higher than the previous one in 2013."
Kapiti, Horowhenua, Whanganui and Taranaki are among the worst affected areas after the storm, that brought heavy rain and snow to much of the South Island yesterday, moved north last night.
About 50 people have been evacuated today in Whanganui and another 100 were asked to leave after the state of emergency was declared at 4pm.
Ms Main said some had been put up in hotels but most had chosen to stay with friends and family.
Earlier today, about 20 people in Feilding had left their homes for a welfare centre in the town.
The incident controller at the Manawatu Whanganui regional council Craig Grant said Whanganui and Hunterville remained hotspots but Feilding South was becoming more manageable as the Oroua River declined.
"We're keeping a close eye on river levels at Whanganui and have activated flood barrier crews.
"The Whanganui River is forecast to peak at 15.5 metres at the Pipiriki monitoring site and this is likely to have an impact for Whanganui around 1am tomorrow morning as it coincides with the high tide.
"Steps have been put in place to reduce the flood risk and the New Zealand Army is on site to assist with sand bagging and evacuations as required," said Mr Grant.
The Whanganui District Council said evacuations were under way in Takarangi Street in Putiki and there had also been evacuations in London Street and Alexander Street following ponding in Peat Park and the surrounding area.
Property owners in areas of Anzac Parade and Taupo Quay in the city were also being notified to evacuate.
Earlier, Whanganui residents were warned all floodwaters should be treated as contaminated after sewage and stormwater spills were reported throughout the city.
Manhole covers in Kowhai Park were lifted to allow stormwater and sewage to spill into the park to lessen the impact on nearby properties in Anzac Parade and in the Matarawa Stream catchment.
The public must stay out of the park due to the danger of open manholes.
Taranaki state of emergency due to Waitotara
A state of emergency has been declared in Taranaki because of the flooding threat to Waitotara township in South Taranaki.
The Waitotara River has been rising after today's heavy rain and the flood peak at the township near the coast is likely to coincide with high-tide at approximately midnight tonight.
The evacuation is under way, with buses sent to the Waitotara Hotel to take evacuees to commercial accommodation that has been arranged by Civil Defence.
Taranaki's Civil Defence group told people in Waitotara they should leave with fears about the rising Waitotara river.
But the group's leader David Lean said many did not want to go.
"We would hope that common sense would prevail and we're making every possible effort to ensure that those that really did want to get out did so, and those that wanted to remain in the area knew the consequences of their own decision."
The township has about 60 households.
A Civil Defence Welfare Centre is being opened in Waverley for people from Waitotara who need shelter. It is at the Waverley Community Centre/Waverley Rugby Club in Chester St.
People had been warned to stay way from downtown New Plymouth for the next 24 hours while sewage contamination caused by flooding was cleaned up.
The Taranaki Civil Defence Emergency Management team said Brougham Street had been closed between Devon St and Ariki St.
But it later said the clean-up of the New Plymouth CBD had been going well and it would be business as usual tonight, with restaurants, hotels and other entertainment venues open.
It however advised people to stay away from beaches, rivers and streams for the next three days.
Power supply still a problem
About 1500 customers in the North Island will spend the night without power.
PowerCo said the cuts affected people in Whanganui, Rangitikei and Taranaki.
Its acting network operations manager, Dean Stevenson, said slips and flooding were making it impossible for field crews to get out for repairs.
About 75 households are also without power in New Plymouth, but should have it back on shortly.
Widespread road closures
The Transport Agency urged people to avoid travel around the lower North Island, if possible.
There are numerous road closures, with just one route for traffic heading north out of Wellington and that's via State Highway 2 to Hawke's Bay.
There was widespread surface flooding across Taranaki, with multiple road closures.
People were advised not to travel unless absolutely necessary, and to take extra care if they did need to be on the roads.
Conditions south of Hawera were marginal and there were closures further south. Awakino Gorge remains open at this stage.
Meanwhile, Whanganui was virtually cut off with not only numerous slips affecting rural roads but state highways to the north, east and west all reportedly closed or marginal.
The Whanganui District Council also pointed people to its website for more detailed information.