All in all, pretty average weather

Despite last year being New Zealand’s second-warmest year on record, the southern region’s weather was average during December.

Niwa meteorologist Seth Carrier said nearly all of the country experienced a warmer than average or much warmer than average month, but no places in Otago or Southland came close to registering mean air temperatures in the top four of their respective records.

While heavy rain late in the month brought above normal rainfall totals to parts of the upper North Island, amounts varied widely across the country in December.

Rainfall was below normal or well below normal in interior Otago, and near normal rainfall was observed in Southland.

No southern locations observed their wettest or driest December on record.

Mr Carrier said December 2023 was characterised by higher-than-normal mean sea level pressure located north and east of New Zealand.

This produced more northwesterly airflows than normal, particularly over the North Island.

"This contributed to above average, or well above average, temperatures across nearly all of the country in December.

"Perhaps the most impactful event during the month was a large severe thunderstorm that tracked north across the eastern South Island and lower North Island on December 12, bringing heavy rain, strong winds and large hail."

The nationwide average temperature in December 2023 was 16.9°C.

This was 1.1°C above the 1991-2020 December average from Niwa’s seven station temperature series which began in 1909, making it the 13th-warmest December on record.