December 2024 was characterised by lower than normal mean sea level pressure (MSLP) over and surrounding Aotearoa New Zealand. This produced more easterly airflows than normal, particularly over the South Island, with more southwesterly airflows than normal over the upper North Island. It was a warm month overall, with above average (0.51°C to 1.20°C above average) or well above average (>1.20°C above average) temperatures throughout the country. The nationwide average temperature in December 2024 was 17.4°C. This was 1.5°C above the 1991-2020 December average from NIWA’s seven station temperature series which begins in 1909, making it the 5th-warmest December on record.

Rainfall was above normal (120-149% of normal) or well above normal (>149% of normal) in eastern and southern parts of the North Island from Gisborne to Wellington, inland Marlborough, northern, eastern and central parts of Canterbury, parts of the West Coast from Greymouth to Hokitika, and central and eastern parts of Southland. Below normal (50-79% of normal) or well below normal (<50% of normal) rainfall was observed in northern, central and western parts of the North Island, Nelson, Tasman, southern Canterbury, and North Otago. Near normal rainfall (80-119% of normal) was observed elsewhere.

Further Highlights:

• The highest December temperature was 34.8°C, observed at Kawerau on 29 December. • The lowest December temperature was -0.2°C, observed at Waipounamu on 17 December, Waipara on 18 December, and Cass on 19 December.

• The highest 1-day rainfall was 140 mm, recorded at Milford Sound on 10 December. • The highest wind gust was 196 km/h, observed at Cape Turnagain on 5 December. • Of the six main centres in December 2024, Auckland was the driest, Dunedin was the coolest and least sunny, and Tauranga was the warmest, wettest and sunniest.

• Of the available, regularly reporting sunshine observation sites, the sunniest four regions in 2024 were Marlborough (2769 hours), wider Nelson (2760 hours), Bay of Plenty (2734 hours), and Tasman (2665 hours).

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