Bay of Plenty and Coromandel are in the firing line as torrential rain, a remnant of deadly Cyclone Debbie, moves over the country.
Heavy rain has caused slips, rising rivers and road closures throughout the North Island over the last 24 hours, and is set to continue for some time yet.
NIWA said the "tropical torrent" could bring two to three times the amount of normal rainfall for the entire month of April in just a couple of days.
Whanganui and Rangitikei councils have declared local states of emergency.
MetService meteorologist Eric Brenstrum told Morning Report more rain was expected as another cloud mass in the Tasman Sea moved over the country.
There had been a bit of a pause in the rain overnight, but more rain was coming for the central North Island and Auckland today.
From Northland to Whanganui including Coromandel, Bay of Plenty, the Central North Island high country, Gisborne, Hawke's Bay, Wairarapa and the Kaikōura Coast, should all get heavy rains.
More than 250mm could fall in some areas with hourly rates of up to 45mm possible.
And strong winds - with gusts up to 120km/h - were expected in the central North Island, Kāpiti, Horowhenua, Nelson and Buller.
Mr Brenstrum said Bay of Plenty and Coromandel were likely to get the most rain.
NIWA meteorologist Chris Chris Brandilino said heavy rain was still falling in Coromandel and Whitianga, but there would more heavy rain and thunderstorms coming for the North Island this afternoon.
And he said people needed to watch out for strong wind gusts.
In the next 24 hours, areas around Whakatane, Tauranga and Rotorua could see some significant falls, with localised heavy falls in Whangaparaoa, Waiheke Island.
"In Wellington, the rain is really going to ramp up later on today and tonight, they could see a fair drop of rain."
Canterbury, from Kaikōura down to Oamaru could have heavy rain and strong winds tomorrow, Mr Brandilino said.