Long-range outlook: What weather’s in store for NZ for the rest of summer?

• Niwa’s just-released outlook is picking above-average temperatures for the North Island over January to March
• In the South Island, there’s an even chance of temperatures being near average or above average over the period
• Westerly flows that have been dominant over 2024 are likely to continue

The year might have started off on a bum note for much of the North Island – but Niwa’s just-issued outlook is picking above-average warmth for the next three months.

But that’s likely to come with a mixed bag of late-season subtropical deluges and dry spells, with the absence of a strong climate driver making for more variable weather around the country.

After what was New Zealand’s fourth-hottest December, temperatures have taken a plunge over the opening days of the year – resulting from a chilly and unseasonable southerly shift.

Fortunately, that glum pattern wasn’t expected to hold throughout the rest of summer, with temperatures likely to be above average for the whole of the North Island.

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In the South Island, there was an even chance of temperatures being near average or above average.

Source / Niwa

However, with more westerly winds likely in the coming months, there could be more frequent spells of cooler weather – particularly in the south.

Elsewhere, the outlook found rainfall was likely to vary around the country.

After a relatively dry start to the year – meteorologists have been closely watching expanding dryness across the top half of the North Island – Niwa warned of a higher risk of subtropical rainmakers visiting later in the season.

“Thus, the risk of occasional heavy rain events remains distinctly possible, particularly as the season progresses.”

The west and east of the South Island were likely to remain relatively dry, but for most of the country, there are equal chances of normal or above-normal rainfall this summer.

While it was still possible that La Niña could form – the climate pattern is known for bringing warm, wet and muggy conditions to New Zealand’s north-east – the likelihood had fallen from 60% to 40%.

Source / Niwa

Instead, neutral conditions – neither La Niña nor El Niño – were more likely, meaning New Zealand could continue to see more westerly flows that have shaped our weather over much of the past year.

“However, this pattern is expected to be interspersed with easterly quarter air flows, especially during periods of La Niña-like weather.”

The outlook comes as Niwa revealed last year was New Zealand’s 10th warmest on record, with the remnants of El Niño and colder seas helping to keep the average temperature slightly below those record-hot results of recent years.

Globally, though, 2024 was likely to be confirmed as the planet’s hottest ever, after another year of catastrophic flooding, scorching heatwaves with temperatures exceeding 50C, and devastating wildfires.

Jamie Morton is a specialist in science and environmental reporting. He joined the Herald in 2011 and writes about everything from conservation and climate change to natural hazards and new technology.

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