Modern Zealand experienced an “extremely active” summer, shaped by volatile weather and driven by a weak to moderate La Niña, according to Earth Sciences New Zealand’s seasonal climate summary.
A Summer of Extremes
The country saw generally westerly or southwesterly winds across the North Island and southeasterly winds in the South Island, dominated by a cyclonic flow. This pattern fueled severe storms, record-breaking rainfall, and destructive winds impacting communities from Northland to Canterbury.
January and February brought particularly intense weather events. On January 21, Tauranga Airport recorded 274mm of rainfall – its highest on record. Several locations in Whitianga, Hicks Bay, Te Puke, and the Coromandel also experienced their heaviest or near-heaviest daily rainfall totals.
Tragically, January’s weather resulted in nine deaths: six in a landslide at a Mt Maunganui holiday park, two when a landslide struck a house in Papamoa, and one when a vehicle was swept away by flooding near Warkworth. A storm in mid-February then impacted the central North Island, looping back to affect the lower North Island, the East Coast, and Canterbury, damaging state highways, causing evacuations, and resulting in one fatality in floodwaters between Pirongia and Ōtorohanga.
Although the average summer temperature nationally was only 0.1°C above normal, the extremes were significant. Parts of Gisborne and Coromandel were “well above average” (more than 1.2°C above average), while the Southern Alps and parts of Otago were “below average” (0.51-1.2°C below average). Napier recorded the country’s highest temperature at 36.8°C on January 11, while Winchmore in Canterbury experienced its coolest summer on record, 1.8°C below average.
Five of the six main centres experienced above-normal rainfall, with Tauranga recording “well above normal” rainfall at 517mm. Wellington and Christchurch also saw “well above normal” rainfall, at 157% and 175% of their typical summer totals. Auckland and Tauranga were the only main centres with above-average temperatures.
Looking Ahead
Earth Sciences NZ climate atmosphere and hazards manager Nava Fedaeff stated that New Zealand is already experiencing the impacts of a warmer world. She indicated that the projections for the future climate suggest more frequent and intense rainfall events. It is tough to immediately determine the extent to which climate change contributed to specific events, but attribution studies may provide further clarity.
Warm sea surface temperatures also played a role, providing energy for subtropical systems. Fedaeff explained that climate change is “exacerbating” existing weather patterns, leading to increased “seesawing” between dry and wet, or cold and warm conditions.
Frequently Asked Questions
What drove the extreme weather this past summer?
A combination of factors, including lower than normal air pressure, a weak to moderate La Niña, and warm sea surface temperatures, contributed to the volatile weather experienced across New Zealand this summer.
How many people were killed as a result of January’s weather events?
Nine people were killed in January, including six in a landslide at Mt Maunganui, two in a landslide in Papamoa, and one when a vehicle was swept away in flooding near Warkworth.
What was the highest rainfall total recorded during the summer?
Akaroa received 563mm of rainfall, which was 333% of its normal summer rainfall, primarily from the storm in mid-February.
As New Zealand continues to experience a changing climate, what role will preparation and adaptation play in mitigating the impacts of increasingly extreme weather events?
