Niwa Lauder climate scientist Gregor Macara said January was characterised by lower-than-normal mean sea-level pressure to the east of New Zealand, which brought more southeasterly airflows than normal.
‘‘This contributed to temperatures that were below average or well below average across much of the country, including eastern Otago and inland Southland.
‘‘In contrast, temperatures were above average or well above average throughout the West Coast and Fiordland.
‘‘Temperatures were near average in western and central Otago and southern Southland.’’
Mr Macara said Dunedin’s year got off to a cool start with a mean monthly temperature of just 14.6°C (0.6°C below average).
Despite the cooler-than-average temperatures, it was a relatively sunny month in Dunedin (256 sunshine hours) and Invercargill (260 sunshine hours) and both cities recorded their third-highest and fourth-highest January sunshine totals, respectively.
They also had more sunshine hours than Christchurch (214 hours) and Wellington (231 hours).
Sunshine was also abundant for western parts of the South Island, Mr Macara said.
‘‘Hokitika recorded 328 hours of sunshine, making it the town’s sunniest January since records began in 1912.
‘‘Farther north, Greymouth recorded 302 hours of sunshine, which was the town’s highest January sunshine total since records began in 1947.’’
Mr Macara said regular spells of southerly winds meant daily maximum temperatures below 20°C were a common occurrence for eastern parts of the South Island.
But at the same time, the ‘‘unusually high frequency’’ of southeasterly winds created a warm month for western parts of the South Island, due to the foehn effect caused by air flowing the opposite way over the Southern Alps.
‘‘Typically, New Zealand’s prevailing westerly airflow means the foehn effect brings relatively high temperatures to eastern parts of the South Island, but these were notably lacking during January 2025.’’
He said New Zealand’s warmest location compared to normal was Greymouth, where the mean temperature of 17.6°C was 1.8°C higher than normal.
Nationwide, the average temperature in January 2025 was 16.4°C, which was 0.8°C below the 1991-2020 January average from Niwa’s seven station temperature series which began in 1909.
That made it New Zealand’s coldest January since 2017.
Mr Macara said it was a dry month for many parts of the country, particularly for the West Coast, much of Southland, and southern and inland Otago, where rainfall totals for the month were below normal or well below normal.
Totals were generally near normal elsewhere.
‘‘Oban [Stewart Island] recorded 27mm of rain, making it the town’s driest January since records began there in 1975.
‘‘It was also a very dry month for the villages of Mt Cook and Franz Josef, where monthly rainfall was just 14% and 19% of normal respectively.’’
At the end of January, soil moisture levels were lower than normal for the West Coast and Stewart Island, higher than normal for central Southland, and about average elsewhere.
