The 'remarkable stats' behind North Island's washed out summer

NIWA meteorologist Ben Noll today said, "if you felt like you didn't really have a summer in the North Island, you were right".

His comments are backed up by some "remarkable statistics" which outline the reason many Kiwis were left wanting a refund on summer 2022/23.

Northland had more than 75% of its annual rainfall in the last three months, Noll said in a video briefing.

"That was experienced right across the North Island," he said.

Parts of the North Island received at least 400% of their normal February rainfall, NIWA said in its monthly climate summary released today.

It was 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.

The highest one-day rainfall total was 316mm, which was recorded in Tūtira, Hawke's Bay, on February 13.

What may come as a surprise to some is that it was also the third warmest summer on record, as 65 locations around the motu experienced record or near-record warm minimum temperatures.

"Humid nights made the summer somewhat warmer overall," Noll explained. "But a lot of folks were sleeping at night so they didn't really feel that warmth."

Down south people definitely noticed the warmth more, as it was the fifth driest summer on record for the South Island. This left many regions parched, with rainfall totals below (50-79%) or well below normal (<50%), as was seen in Fiordland.

"Meteorological drought developed in Otago during February, with many areas recording less than half of their normal summer rainfall," NIWA said in its climate summary.

It wasn't just hot on the land, in the north and east of the South Island, summer sea surface temperatures were the second highest on record.

NIWA also released a list of the sunniest locations in 2023 so far:

• Central Otago (562.6 hours)

• West Coast (548.6 hours)

• Mackenzie Basin (545.4 hours)

• Queenstown Lakes District (526.7 hours)

NIWA this week also gave its Autumn forecast with cooler weather on the horizon as La Niña — which brought heavy rains to the northeast of the North Island and dry conditions down south — transitions to ENSO-neutral during March.

The transition to a neutral state means the country can expect to see more variable air flow, temperature and rainfall patterns during autumn, NIWA said in its seasonal outlook.

It will also see low pressure occur more frequently over the Tasman Sea and the South Island in March, resulting in spells of westerly winds and, in turn, more cold fronts typical of the cooler autumn months.

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Low pressure systems to the west of both islands are also expected to lead to rainfall, gradually easing the rainfall deficits in the parched west and south of the South Island.

From March to May, seasonal temperatures are most likely to be above average in the west of the South Island and about equally likely to be near average or above average elsewhere, cold spells will become more common, such as during early to mid-March. It's also expected to be accompanied by an increasing risk for frosts.