Official Niwa climate data shows the nationwide average temperature for winter 2020 was 9.6degC — 0.06degC warmer than the previous record set in 2013.
Forecaster Ben Noll said the data comes from Niwa’s Seven Station Temperature Series, which began in 1909, and showed the 2020 winter was 1.14degC above average.
This year’s result also meant seven of the 10 warmest winters on record in New Zealand have occurred since 2000.
Seventeen locations recorded their highest winter mean air temperatures since records began.
Haast, Milford Sound, Puysegur Point and Alexandra recorded their second-highest, and Oamaru, Dunedin and Five Rivers recorded their third-highest mean air temperatures.
The highest recorded winter 2020 temperature was 25.1degC on August 30 in Timaru.
It was the highest temperature recorded there during winter since records began in 1885, and the fourth-equal warmest winter temperature on record for New Zealand as a whole.
Oamaru also recorded its highest winter temperature when the mercury hit 23.2degC on August 30; and Puysegur Point, Wanaka, Ranfurly, Dunedin Airport and Dunedin (Musselburgh) posted their second-highest.
The lowest temperature of the winter was -12.3degC, recorded in Middlemarch on June 14.
Surprisingly, the highest one-day rainfall did not occur in Milford Sound this winter.
It was recorded in Kaikohe and Whangarei, which received 262mm and 251mm respectively on July 17.
This is the highest one-day rainfall observed for both locations during winter.
Of New Zealand’s six main centres, Dunedin was the driest, Auckland was the warmest, Christchurch was the coolest, Hamilton was the least sunny and Tauranga was the wettest and sunniest.
Mr Noll said the winter warmth could be attributed to several factors.
Firstly, there were more sub-tropical northeasterly winds than normal, which brought warmer air toward New Zealand from the north.
Sea-surface temperatures (SST) were above average during winter, especially August, and because New Zealand is an island nation, air temperatures are strongly influenced by the seas surrounding it.
Air pressure was also higher than normal, especially to the east, which contributed to a sunnier-than-usual winter in much of the South Island and lower North Island.
And climate change played an ongoing role because it was consistent with New Zealand’s long-term trend of increasing air temperatures, he said.
