A MetService temperature map of New Zealand as the heat reached "alert levels" on 12 December. Photo: MetService
December temperatures were warmer than average across nearly all of the country, according to NIWA's latest monthly report.
The average nationwide temperature was recorded at 16.9C, 1.1 degrees warmer than the average December temperature between 1991 and 2020.
The results from the institute follows a 12 month snapshot released on Wednesday that concluded 2023 as the "second hottest year on record".
Last month, temperatures were predominantly above average (0.51C-1.2C) or "well above average" (1.2C+).
Only parts of coastal Wellington, Marlborough Sounds and Southland experienced temperatures on par with the average December.
The highest temperature for December was when 33.7C was recorded at Hanmer Forest on 20 December, while the lowest was the -0.6C observed at Manapouri on 1 December.
NIWA (The National Institute of Water and Atmospheric Research) confirmed last month was the 13th warmest December since records began in 1909.
Whilst the warmer temperatures painted a consistent picture across the board, rainfall levels fluctuated throughout both islands.
Rainfall was above normal (120-149 percent) or well above normal (over 149 percent in western Northland, much of Auckland, western and interior Waikato, Gisborne, and much of the West Coast.
But rain was recorded below or well below average levels in eastern Northland, parts of the Coromandel and Bay of Plenty, southern Hawke's Bay, Manawatū / Whanganui, Wairarapa, Nelson, Marlborough, northern and inland Canterbury, and inland Otago.
Other regions were on par.
The report highlighted the severe storm on 12 December that struck eastern parts of the South Island and lower North Island, that brought heavy rain, strong winds, and large hail.
"Wellington's Hutt Valley was particularly hard-hit, where multiple buildings were severely damaged by strong winds, localised flooding and hailstones up to 12 mm in diameter were observed, and more than 2000 properties were left without power," the report said.
A strong oceanic El Niño was also recorded during December, although "unusual ocean heat" in the western Pacific and globally added to air pressure and circulation patterns that are not historically linked with El Niño, nor variable rainfall patterns in New Zealand.
