Winter 2023

04 September 2023

A warm and dry winter for many parts of the country

Temperature	Temperatures were above average (+0.51°C to +1.20°C of average) for western parts of Southland, coastal Otago, eastern and inland parts of southern and central Canterbury, Nelson, Tasman, and coastal Hawke’s Bay. Temperatures were generally near average (±0.50°C of average) for the remainder of the country.
Rainfall	Rainfall was below normal (50-79% of normal) in parts of Northland, Auckland, Taranaki, Whanganui, the Central Plateau, Wellington, Tasman, Nelson, West Coast, Marlborough, inland Canterbury, and inland Otago. In contrast, rainfall was above normal (120-149% of normal) or well above normal (>149% of normal) rainfall in southern parts of Southland, eastern Otago, eastern Canterbury, and southern parts of Gisborne.
Soil moisture	At the end of winter, soil moisture levels were near normal for most of the country. Above normal soil moisture was observed in isolated areas inland of Dunedin, with below normal soil moisture observed for southern parts of the Mackenzie Basin.

Overview

Winter 2023 began on a warm note, with Aotearoa New Zealand observing its 5th-warmest June on record. The unusual warmth continued into the middle part of the season, with the country registering its 4th-warmest July on record. In contrast, below average temperatures were observed for August. Overall, the nationwide average temperature for winter was 9.2°C, 0.6°C above the 1991-2020 average from NIWA’s seven-station temperature series which begins in 1909. This ranked as New Zealand’s 5th-warmest winter on record.

It was a relatively dry season for many parts of the country, with a considerable reduction in the number of rain-bearing storms arriving from the north of the country compared to earlier in the year. Mean sea level air pressure was lower than normal to the east of the North Island during winter overall, resulting in slightly more southerly airflows than usual, mainly in the North Island. These air pressure and wind patterns were influenced by a decaying La Niña at the start of winter, and a developing El Niño by the end of the season. Although winter was dry for many, several exceptional rainfall events occurred during June and July. Most notable was the 22-24 July rainfall event that primarily impacted Canterbury. During this event, Christchurch, Akaroa, Leeston and Woodend each observed their wettest winter day on record (see Highlights and extreme events section for further details).

The prevalence of early-winter warmth resulted in a slow start to the ski season across the country. Both Mount Hutt (Canterbury) and Coronet Peak (Otago) were forced to temporarily close in June, with a lack of suitable weather for either natural or artificial snow production. Regular snowfalls during August meant that conditions improved markedly across New Zealand’s ski areas.

Further highlights for winter 2023:

The highest temperature was 24.0°C, observed at Whakatu on 2 June.
The lowest temperature was -10.6°C, observed at Tara Hills on 10 June.
The highest 1-day rainfall was 199 mm, recorded at Akaroa on 22 July.
The highest wind gust was 180 km/h, observed at Cape Turnagain on 1 and 16 July.
Of the available, regularly reporting sunshine observation sites, the sunniest four regions in 2023 so far are wider Nelson (1644 hours), Mackenzie Basin (1617 hours), Taranaki (1605 hours) and Tasman (1586 hours).
Of the six main centres in winter 2023, Auckland was the warmest, Tauranga was the sunniest and wettest, Christchurch was the coolest, and Dunedin was the driest and least sunny.