The remnants of ex-cyclone Ita are set to sweep across the upper North Island today, bringing heavy rain and gales, while the rest of the country is also in for a soaking.
The MetService has warned the weather system has all the hallmarks of the remnants of Cyclone Lusi which struck more than a month ago.
The ex-cyclone is one of two main weather systems bringing wet weather to the country, with the other system moving across the Tasman Sea.
Severe weather watches are in place for Northland, Auckland, Coromandel, Taranaki, , Nelson, Marlborough and Southland.
Heavy rain was also soaking Wellington, where Prince William and his wife Catherine are being farewelled today.
Heavy rain warnings were in place for the ranges of northwest Nelson, the Richmond Range, western parts of Marlborough Sounds and Mt Taranaki.
In the South Island and lower North Island, bands of rain were being fuelled by a broad, slow-moving area of low pressure over the Tasman Sea.
In the north of the North Island, rain and gale northeasterlies were expected later today as the remnants of ex-cyclone Ita moved into the north Tasman Sea.
The MetService said about 100-120mm of rain was expected about the northwest Nelson Ranges, Richmond Range and western parts of Marlborough Sounds.
On the upper slopes of Mt Taranaki, 150-200mm could fall in a 20-hour period today.
The MetService said rainfall could also approach warning amounts about eastern parts of Northland, Auckland and Coromandel Peninsula tomorrow, with northeasterly gales possibly becoming severe for a time.
In eastern parts of Northland, the ex-cyclone could bring 100mm of rain and wind gusts of 100km/h.
WeatherWatch said the remnants of Ita would bring rain to parched areas around the North Island, including Northland, Auckland, Waikato and Manawatu.
The low would stall or slow down over the Tasman Sea, making for slower-moving rain bands that would improve rainfall in dry regions.
However, the rain may become very heavy for the upper South Island, while gales may become damaging in some western areas. Central New Zealand and the western South Island may be most exposed to damaging gusts.
The Fire Service's northern region has a "standing army" to deal with emergencies and Far North area manager Allan Kerrisk said his crews were prepared.
However, it was unlikely that crews would be deployed from outside Northland, such as those sent during Cyclone Lusi.
Northland Regional Council deputy harbour master Chidambaram Surendran has advised sea-goers to check the marine forecast before venturing out to sea and to keep a close eye on boat moorings.
Bill Hutchinson, of Far North Civil Defence, said he was keeping a close eye on the storm but so far the MetService had
only issued a severe weather watch for Northland, not a warning.