After the northern hemisphere sweltered through the hottest summer in human history, New Zealand’s usually cool start to spring has also hit record high temperatures that are usually reserved for its summer months.
The country recorded its hottest September on record, with every region in the country experiencing above-average temperatures, with one area hitting 29.6 C.
Data from the National Institute of Water and Atmospherics (NIWA) shows the nationwide average temperature was 11.9C, 1.3C warmer than the 1991-2020 September average and the hottest since records began in 1909.
Of the six main centres in September 2023, Auckland was the warmest, Tauranga the sunniest, Dunedin the driest, Wellington the wettest and least sunny, and Christchurch the coolest.
Wairoa, on the North Island’s east coast, reached 29.6C on September 21st – the highest September temperature on record for the North Island, and New Zealand’s third-highest for the month since records began.
In the South Island, some locations set new record high daily maximum temperatures, including Oban in Stewart Island, which hit 23.5C, 6 degrees higher than its normal daily maximum temperature for February – the height of New Zealand’s summer.
“In Oban, 23.5C would be quite an exceptionally warm day in summer down there, let alone in September,” says Gregor Macara, a climate scientist at NIWA.
Last week, NIWA officially declared the arrival of El Niño conditions. The weather pattern tends to bring warmer winds from the west and north-west, which can lead to drier conditions on the east coast.
“Sydney has been getting some exceptionally high temperatures into the mid-30s and some of those warmer air masses have been blown over the Tasman Sea to New Zealand,” Macara said.
El Niño is likely to continue over summer, which could contribute to periods of unseasonable warmth, followed by sudden chilly weather. Some regions in the west could experience increased rainfall and flooding, while others in the east could be at risk of drought, Macara said.
The switch from La Nina – which brought with it New Zealand’s worst weather event this century, Cyclone Gabrielle – to El Niño could bring some relief to the regions that were drenched with record-high rainfall and devastating floods.
“Places like Auckland have already had more than their usual year’s worth of rain some months ago … but we are anticipating those sorts of areas to be drier than they have been,” Macara said.
While El Niño traditionally brings warmer conditions, climate change is “definitely” intensifying the heat, Macara said. “It’s shifting the odds of being in high temperatures because our base temperature is warmer nowadays than it has been in the past.”
