Autumn 2023 was topped off with the warmest May on record, toppling many southern temperature records in the process.
Niwa climate scientist Gregor Macara said the nationwide average temperature in May was 13.1degC — 2.0degC above the 1991-2020 May average from Niwa’s seven station temperature series which began in 1909.
"Of the five warmest Mays on record, all have occurred since 2011," he said.
"The widespread nature of May’s exceptional warmth, both on land and in the sea, have been exacerbated by climate change."
Record daily maximum air temperatures for May were recorded at Franz Josef (23.2degC), Ranfurly (22.7degC), Manapouri Airport (21.3degC), Queenstown (23degC), Cromwell (24degC), Tapanui (23.7degC), Invercargill (23.8degC), Tiwai Point (21.9degC), Oban (20.9degC), Haast (21.5degC) and Balclutha (24.0degC).
Clyde and Gore recorded their second-highest temperatures, and Middlemarch and Nugget Point recorded their third-highest.
Niwa meteorologist Seth Carrier said autumn, as a whole, was New Zealand’s fourth-warmest on record, surpassed only by 2022, 2016, and 1938.
"Autumn 2023 was characterised by higher-than-normal mean sea level pressure (MSLP) east of New Zealand, and lower-than-normal MSLP over New Zealand and the Tasman Sea.
"This generally resulted in more northeasterly winds than normal, bringing moist air from the tropics and sub-tropics across New Zealand, resulting in periods of wet and warm weather."
He said temperatures were above average or well above average across nearly all of the country, but near-average temperatures were observed in interior Canterbury and Otago.
No areas experienced below average autumn temperatures.
Near-record mean air temperatures for autumn were recorded at Oban, Nugget Point, South West Cape, Gore, Dunedin, Invercargill and Tiwai Point.
He said it was also a wet season for large swathes of New Zealand during autumn, and the southern regions were no exception.
A record autumn rainfall total was recorded at Five Rivers (383mm) and Lumsden recorded its second-highest with 363mm.
Mr Carrier said despite the season’s strong wet and warm lean, there were a few hints at the colder months to come.
On March 21, snow fell to about 800m above sea level across parts of the lower South Island, and on May 11 a powerful cold front brought the coldest day since October 2022 for large parts of the South Island and snow down to around 400m for parts of Southland, Queenstown-Lakes District, and the Mackenzie Basin.
