The storm is forecast to hit Taranaki with vengeance from midnight tonight. Up to 400mm is expected to fall on Mt Taranaki and 250 mm near the coast in the coming 48 hours.
Niwa says the remnants of Tropical Cyclone Debbie are threatening to develop into a serious situation in the next 72 hours.
Virtually no region in the North Island will escape the potentially damaging impact of the torrential rains. It was also affect districts in the north-east of the South Island.
Tropical downpours are set to saturate Northland and Auckland tomorrow night with Wellington to be drenched by heavy falls on Wednesday.
Astounding levels of rain are forecast to saturate the North Island with 125 mm of rain to fall in Northland, Taranaki and the central plateau by Tuesday night.
In the latest MetService warnings Wanganui is expected to get 250 mm of rain in 33 hours from early tomorrow morning until lunchtime Wednesday.
"This is a significant amount of rain for these areas and people are advised to watch out for rapidly rising rivers and streams, and possible surface flooding and slips," said MetService.
Regions from Coromandel to Nelson have been placed on a watch with heavy rain likely to reach warning levels over the next 48 hours.
Severe gales are also expected to lash southern Taranaki through to Buller on Tuesday and Wednesday.
Niwa forecaster Ben Noll is warning the torrent will be so back it may drop up to three times the normal rainfall for the entire month in just three days.
MetService said the worst weather was reserved for Tuesday and Wednesday with heavy falls across central New Zealand. There would also be strong southeasterly winds that could turn into destructive gales.
WeatherWatch.co.nz said central regions around or near Cook Strait, and those facing towards the Tasman Sea such as Nelson and Taranaki, were at risk of flooding.
Heavy rain would start falling as early as this evening in Taranaki and last until Thursday.
