MetService is warning people to take heed of weather warnings saying conditions could be similar to those experienced during Cyclone Giselle which contributed to the Wahine disaster in 1968.
The country is being warned to prepare for damaging gales, enormous storm and surges and widespread flooding as Cyclone Cook bears down, threatening to plunge regions into chaos.
Although the cyclone has since been downgraded to a extra tropical low, it is still expected to carry a big punch.
Severe weather warnings have been issued in parts of the country as heavy rain started to pound Auckland this afternoon. There have been several reports of flooding around the city already.
Civil Defence issued a warning tonight, describing Cyclone Cook as an "extremely serious weather event".
"Put safety first. Don't take any chances," Civil Defence said.
The MetService has put out a heavy rain warning for Northland, Auckland, Coromandel, Bay of Plenty, Taupo, Waikato, Waitomo, Mt Taranaki, Tongariro NP, Buller, Nelson, Marlborough Sounds, Richmond and Bryant Ranges, North Otago, Dunedin and Clutha.
Meteorologist Andy Best said he was worried people weren't heeding warnings.
He said he'd been working as a forecaster at MetService for about 20 years, and had never seen an event like this one.
"This a very dramatic event."
He said the last weather event to have similar conditions was Cyclone Giselle, which hit New Zealand in 1968 and contributed to the Wahine disaster.
The sinking of the Lyttelton-Wellington ferry Wahine on April 10, 1968 was New Zealand's worst modern maritime disaster, claiming more than 50 lives.
This afternoon Thames-Coromandel District Council Mayor Sandra Goudie has declared a civil defence emergency for the district. Waikato Civil Defence has warned residents to stock up on enough food and water for seven days.
Aucklanders are being told to reconsider travel plans and warned to expect gusts of 140km/h and possible disruptions to transport, particularly ferries and flights, tomorrow.
Great Barrier Islanders are being warned to brace for the worst weather they've seen in recent times.
Auckland Civil Defence head of emergency management operations Aaron Davis said
"The rain, combined with severe wind and coastal storm surge, could create extreme impacts for Great Barrier Island," said Davis.
Heavy rain started to fall over Auckland late this morning and were quickly followed by reports of roads being flooded; causing some traffic congestion, particularly in parts of West Auckland and in North Shore.
Here are the latest areas forecast to be affected by Heavy rain and Severe gales. Detailed information found at https://t.co/iVxgMqrUMa. ^AB pic.twitter.com/ssQQ0SvgdR
— MetService (@MetService) April 12, 2017
Transport authorities urged drivers to stay alert and to keep a safe travelling distance.
Air New Zealand also sent out an advisory to passengers to keep updated via its website about any flights that may be affected by the ex-cyclone.
Many places will see a month's worth of rain fall in the space of a day, while damaging gales could wreak havoc.
Conditions are expected to be so hazardous MetService is advising people to seriously consider altering Easter travel plans.
The flood-ravaged Bay of Plenty is already in a state of emergency as Cyclone Cook advances closer to our shores.
The Ministry of Education has advised all schools and early learning centres in the Eastern Bay of Plenty to remain closed and says there will be further closures in the Franklin area, Great Barrier Island, Waiheke Island, Thames and Coromandel.
At total of 94 schools and 129 North Island early learning centres will be affected.
The MetService is warning after severe flooding in Bay of Plenty last week that the region is looking to be one of the worst-hit areas, with up to 250mm of rain expected to fall in the next two days.
To complicate matters Cook is likely to dump huge amounts of rain at the end of the week, prolonging the rain falling in already devastated areas.
The Easter storm is unwelcome news for many Edgecumbe residents who remain unable to return to their homes swamped in last week's floods. Others living in rural areas are still cut off.
Meanwhile, Whakatane residents flooding a local supermarket and panic-buying groceries are being told there's absolutely no need to do so.
A Foodstuffs spokesperson says there's been a Facebook post in the Whakatane area, claiming that the Pak'n Save is shutting at midday because of the storm. She says this is not true, the supermarket is open for business as usual and will not be closing early.
The supermarket is also bringing in extra supplies to help storm-affected residents.