Cyclone Gabrielle, which killed at least 11 people, will go down in New Zealand's history as one of its worst weather disasters, NIWA says.
The cyclone caused historic extreme rainfall and river flooding, catastrophic wind damage, and substantial storm surges across the North Island.
Parts of the North Island received at least 400% of their normal February rainfall, NIWA said in its monthly climate summary.
Napier saw over 600% of its normal rainfall totals in February — its third wettest month since records began.
The highest one-day rainfall total was 316mm, which was recorded in Tūtira, Hawke's Bay, on February 13.
Meanwhile, parts of the South Island were left parched, with rainfall totals below (50-79%) along parts of the northern West Coast and well below normal (<50%) in Canterbury and coastal Otago, with an area of well below normal rainfall (<50% of normal) in Fiordland.
It was also the second wettest summer on record for the North Island, with the Auckland region receiving over 5.5 times its normal summer rainfall and 63% of the entire annual normal.
It was the wettest summer on record for several major centres, including Napier, Auckland, Whangārei, Gisborne and Tauranga.
It was the fifth driest summer on record for the South Island.
In addition, 18 locations saw a record or near-record high summer wind gust.
The highest wind gust was 150 km/h, and was observed at Mokohinau Islands on February 12.
Third warmest summer on record

While February 2023 saw large swathes of the North Island hit with a deluge, summer temperatures were also on the rise.
The nationwide average temperature last month was 18.5C — 1.1C above the 1991-2020 February average.
Temperatures in the West Coast were sweltering, with February being the warmest on record for Greymouth, Westport, and Arapito.
Greymouth was the most hard-hit, with seven days recording a daily maximum temperature above 25C. Between 1972-2000, the town had just six days in February where the temperature exceeded 25C.
The highest temperature was recorded in Middlemarch, Otago, on February 4, after temperatures rose to 35.6C.
It means last month was New Zealand's 10th-warmest February on record.
This summer was also the third warmest on record, after 65 locations experienced record or near-record warm minimum temperatures.
Central Otago the sunniest region in the country
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People looking for a serotonin boost should look no further than Central Otago.
The South Island district was the sunniest location so far this year after seeing 562.6 hours of sun.
It was followed by the West Coast with 548.6 hours.
Mackenzie Basin came in third with 545.4 hours.
Queenstown Lakes District, meanwhile, came in fourth with 526.7 hours.
The hours of sunshine in Hokitika were twice the amount seen in Dannevirke and Dargaville.
Record-breaking marine heatwave
Summer sea surface temperatures were record-breaking in the west of the South Island.
The summer sea surface temperatures were the second highest on record in the north and east of the South Island.
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