The storm is forecast to move southeast across the centre of the country tonight.
In its latest update MetService says the heaviest rain is expected about Mt Taranaki, Tongariro National Park, the Bay of Plenty ranges and Marlborough.
Destructive gales will continue to batter the North Island and north Canterbury today and tomorrow.
Metservice warns that on top of today's coastal flooding in northern regions from king tides, western and southern areas are at risk, especially along Wellington's south coast tonight.
King tides, gales and driving rain continue to cause widespread damage across the upper North Island.
Thousands are still without power as trees and powerlines topple in the hurricane-strength winds blasting the island.
The Hauraki District Council this morning advised people in low-lying areas of Kaiaua village and on East Coast Rd to urgently evacuate to higher ground because of the king tide.
Firefighters are helping residents and civil defence crews are also on their way to help with the evacuation.
East Coast Rd is now closed by rising floodwaters.
Major roads, including Auckland's Northern and Northwestern Motorways and Coromandel's SH25 were impacted by flooding this morning. Many other roads across the upper North Island are partially blocked by slips and downed trees.
Two southbound lanes of Auckland's Northern Motorway and an eastbound lane on the Northwestern Motorway at the Causeway were earlier closed because of flooding. All had since reopened.
A pontoon at Halfmoon Bay was smashed by the bad weather.
Coastal roads went under water - some for the third time in 24 hours - as king tides were swollen even more by storm surges.
Police closed the Thames Coast Rd because of debris and rocks being washed onto lanes by the incoming tide.
An evacuation centre has been opened at Te Puru, north of Thames, for those whose homes are underwater or motorists stranded by the flooding.
Auckland's Tamaki Dr is impassable and is closed again this morning.
Vehicles are also stuck in floodwaters in Auckland and Christchurch anmd a bus is stranded on Tamaki Dr near Kohimarama.
The swirling storm, which is sitting off the west coast of the North Island, is due to hit Taranaki at midday.
It will then track over the island for the rest of the day before clearing the country's eastern coastline on Saturday.
Niwa says the upper and western regions of the North Island will continue to be hammered by storm-force wind gusts and rain until this afternoon.
Record levels of rain have fallen in the past 24 hours with 41mm falling in Auckland since 9am yesterday - more than all of November and December combined.
The Gisborne region has been deluged overnight when a whopping 200mm falling on the eastern tip of the North Island.
Tairawhiti Civil Defence said 208.5mm was recorded at Waikura in the past 24 hours and 189.4mm fell at Rip, 178.5mm at Oweka and 124mm at Pakihiroa.
About 30,000 households and businesses across the North Island have been hit by power cuts in recent hours as strong winds bring trees down on power lines.
The strong winds have left a trail of debris across Auckland, causing more than $100,000 of damage on Awhitu Peninsula, near Manukau Heads.
The overnight chaotic weather has flooded houses, cars and broke down a sea wall.
Aucklander Will Hay, who is holidaying at his family bach on Hudsons Beach, was woken at 2.30am by the storm. Outside a 4.5m king tide had flooded baches and cars - including two Audis.
Hay estimated the water came 60m further that usual. Most damage was to the sea wall where the water had eaten sand and earth away on both sides.
"There's been huge erosion overnight and the sea wall couldn't stand up to the waves and winds.
"It's pretty bad. Our section is about 250m long and there's not one spot on the wall that's still relatively intact, it's all pretty smashed up.
Hay said the next high tide was due at 2.30pm and locals were nervous the flooding would repeat.
The sea wall cost about $70,000 to erect a decade ago and would likely need to be fully replaced, Hay said. He estimated that along with the flood damage to homes and cars that could be written off the damage would come in around $150,000.
