Winter 2020: NZ's warmest on record

Author
Michael Neilson, NZ Herald,
Publish Date
Thu, 3 Sep 2020, 3:35PM
The biggest snowfall this year came on the first day of spring, as seen here in Naseby on Tuesday. Photo / Otago Daily Times
The biggest snowfall this year came on the first day of spring, as seen here in Naseby on Tuesday. Photo / Otago Daily Times

Winter 2020: NZ's warmest on record

Author
Michael Neilson, NZ Herald,
Publish Date
Thu, 3 Sep 2020, 3:35PM

If you felt like the big chill never arrived this year you'd be correct; according to Niwa, it's been New Zealand's hottest winter on record.

Seven of the 10 warmest winters have occurred since 2000, increasingly fuelled by climate change - the "long-term tailwind".

The countrywide average for 2020 was 9.6C - 1.14C above the 1981-2010 average, taken from Niwa's seven station temperature series which begins in 1909, and pipping the previous record of 2013 by just 0.06C.

Temperatures across the country were generally above or well above average. Only a few spots were near average, including Tararua, Kaikoura, and parts of Southland and Otago.

The top spot was Timaru, with a completely out-of-season 25.1C on August 30.

The lowest temperature was -12.3C, at Middlemarch on June 14.

Of the six main centres in winter 2020, Auckland was the warmest, Christchurch was the
coolest, Tauranga was the wettest and sunniest, Dunedin was the driest, and Hamilton was the least sunny.

The most rainfall in one day was 262mm, recorded at Kaikohe on July 17, and the highest wind gust was 191km/h, at Cape Turnagain on July 23.

New Zealand's average winter temperatures since 1909. Image/ Niwa
New Zealand's average winter temperatures since 1909. Image/ Niwa

According to Niwa's Winter 2020 Climate Summary, driving these high temperatures were four main factors: sub-tropical winds, warmer-than-average seas, more sunshine, and climate change.

The season was characterised by more frequent warm northeasterly winds than normal, particularly to the North Island, which was associated with a developing La NiƱa event in the equatorial Pacific.

Sea surface temperatures (SSTs) surrounding New Zealand were also warmer than average - 0.5C to 1C - and most notably during August, which exerted a further warming influence on the country's air temperatures.

A prevalent high-pressure system over the country contributed to a sunnier-than-normal winter for much of the South Island and lower North Island.

This all combined with the background influence of climate change, the "long-term tailwind to our temperatures", which resulted in widespread warm conditions during winter.