New Zealand’s average annual temperature has risen 1.36 degrees Celsius since national records began, and every one of the country’s 30 long-running climate stations is now warmer in winter than it was in the early 1970s, according to a batch of environmental indicators released by Stats NZ on Friday 2 October.
The same release shows carbon dioxide, methane and nitrous oxide all reached their highest recorded concentrations last year at the Baring Head monitoring station on Wellington’s south coast. The indicators cover data to the end of 2025 and are drawn mostly from 30 climate stations run by Earth Sciences New Zealand, the Crown research institute formed from NIWA and GNS Science.
Stats NZ publishes the indicators as part of a joint environmental reporting programme with the Ministry for Cities, Environment, Regions and Transport.
The national temperature figure comes from Earth Sciences New Zealand’s long-running “seven-station” series, which starts in 1909. Over the 117 years to 2025, the temperature indicator shows a rise of 1.36°C. The warmest year on record remains 2022, which averaged 13.76°C, or 1.02°C above the 1991 to 2020 baseline of 12.74°C. Seven of the 10 warmest years have come since 2016, and the last year to come in below the baseline was 2012.
Stats NZ adds a caution of its own. The 1.36°C figure is a straight-line trend across more than a century, and because the real path of temperatures has not been a straight line, the agency says the estimate “may understate or overstate rates of warming throughout the series.”
At the 30 individual stations, which have comparable records from 1972, average annual temperatures were very likely rising at 29 sites. Winter was rising at all 30. Spring changed least, with increases at 26 sites.
“Across the country, average temperatures are rising fastest in winter and slowest in spring,” Stats NZ environment statistics spokesperson Tehseen Islam said. “Increasing temperature can impact agriculture, energy demand, ecosystems, recreation, and human health.”
Warmer winters show up most clearly in the frost count. Of the 27 stations where frosts are recorded, the number of frost days has very likely fallen at 17 and risen at only two since 1972, the frost indicator shows. Tara Hills near Omarama is still the frost capital, averaging 106 frost days a year over the decade to 2025, while Auckland, Wellington, Whangaparāoa and Whangārei recorded none at all. At the other end of the scale, warm days above 25°C have very likely become more common at 22 of the 30 sites.
Rainfall tells a less tidy story. Between 1960 and 2025, nine stations recorded more rain each year and six recorded less. The North Island is a patchwork, with some places getting wetter and others drier, while the South Island is generally getting wetter. Milford Sound, already the wettest of the 30 sites, is gaining about 180 millimetres a decade and now gets more than twice the annual rain of Hokitika, the next wettest station.
“Changing rainfall, especially seasonal changes like the increases in spring, can impact farmers and fisheries,” Islam said. “Changing rainfall patterns can also impact hydro lake storage levels, influencing the capacity to generate and supply hydroelectricity.”
The extreme rainfall indicator measures how much of each year’s rain falls on “very wet days”, defined as days wetter than 95 percent of days at that site between 1991 and 2020. That share has very likely grown at 11 of the 30 stations, by between 0.6 and 1.8 percentage points a decade, and shrunk at three. The biggest single-day downpour of each year has increased at five stations and decreased at four, so the picture on the very heaviest days is still mixed. Stats NZ notes that a warmer atmosphere can hold more water vapour, which is why scientists expect heavier rain events as temperatures rise.
Baring Head, near the mouth of Wellington Harbour, has been sampling the air since 1972. Stats NZ says air reaching the station from the south comes from areas with no human activity, which makes it a good indicator of global background levels.
According to the greenhouse gas indicator, carbon dioxide stood at 423.1 parts per million in December 2025, up 5.5 percent since December 2016, with the all-time monthly high of 423.8 parts per million recorded in September 2025. The yearly increase itself is getting larger, with the average annual growth rate rising by 0.03 parts per million each year between 1973 and 2025. Methane peaked at 1,901.7 parts per billion in September 2025, and its growth rate very likely sped up between 2007 and 2021. Nitrous oxide hit a high of 338.3 parts per billion in December 2025.
Earth Sciences New Zealand principal atmosphere technician Gordon Brailsford told RNZ the speed of the increase was the striking part. “Each decade has a greater growth rate than the previous decade… That’s reaffirmed in the data released today.”
He said the first good sign would be a year in which the concentration grew more slowly than the year before. “If we can build on that, then we can get away from this compounding growth that we’re having,” he said. “What we’re looking at, at the moment, is trends that just continue to go up.”
Stats NZ’s indicator pages say the global rise in temperatures is almost certainly due to greenhouse gases from human activity, citing the Intergovernmental Panel on Climate Change and earlier government reporting. They also note that natural cycles such as El Niño and La Niña push individual years up or down without changing the long-term trend. That matters this spring, with a strong El Niño declared in July and forecasters expecting it to shape New Zealand’s weather into summer.
One other set of numbers in the release may interest anyone planning a holiday. Over the decade to 2025, Richmond near Nelson averaged 2,682 hours of bright sunshine a year, the most of any of the 30 sites, while Balclutha in South Otago averaged 1,686 hours, the least, according to the sunshine indicator.
Has your part of the country noticed fewer frosts or heavier downpours over the years? Share what you have seen in the comments below.
This article was written by AI, briefed to report the facts, hopefully without some of the bias people bring to the job 🙂
Leave a Reply