Stats NZ’s Rainfall: Data to 2025 indicator, published 2 October 2026, examines annual and seasonal rainfall at 30 sites across Aotearoa New Zealand. Over 1960–2025, annual rainfall trends were assessed as very likely increasing at nine sites and very likely decreasing at six. Milford Sound had the largest upward trend, at 180 millimetres per decade. The findings show that long-run rainfall direction is not uniform across the country. They do not describe a single national rainfall total or imply that every location followed the same pattern in each year.

The update also compares average annual rainfall levels during 2016–2025. Milford Sound in Southland and Hokitika on the West Coast had the highest averages among the 30 sites. The lowest levels were found at several Canterbury sites, including Timaru, Tara Hills, and Lake Tekapo. Those are site-based comparisons for the recent ten-year window, distinct from the trend analysis spanning 1960–2025. The release does not give a single figure in its headline for national rainfall volume, and these station observations should not be treated as exhaustive totals for entire regions.

Seasonal patterns differ from annual ones. For spring rainfall, seven sites had a very likely increasing trend, more than in any other season; three sites had a very likely decreasing spring trend. This does not mean the rest of the sites had no change: some trends may have been likely, indeterminate, or in the opposite category. The source’s term “very likely” reflects a statistical likelihood classification. Seasonal totals can vary substantially from year to year, so a long-run direction does not establish that rainfall rose steadily or consistently in every spring.

Stats NZ and the Ministry for the Environment use data supplied by Earth Sciences New Zealand from its National Climate Database. The 30-site network was selected to represent the local climate around measurement locations, more closely reflecting places where many people live than the climate of each whole region. Rainfall records are extended as far back as 1960 where the data permit. Some station series include earlier records from nearby sites. Thus the site network is a set of representative local observations, not a complete gridded gauge census of the country.

For a separate set of map products, Earth Sciences New Zealand supplied annual rainfall estimates from 1972 to 2025 using spatial interpolation, which estimates values where few or no direct observations are available. Stats NZ cautions that the maps show broad patterns rather than precise local conditions and that comparisons across locations or time should be treated carefully. The mapped grid series and direct 30-site trend results have different spatial representations; readers should not assume a map cell is an observed rain gauge or that the two products are interchangeable at a precise location.

Trend direction and likelihood are assessed with the Mann–Kendall test, and Sen slope regression estimates average change per decade. “Very likely” indicates probability above 90%, “likely” above 66%, and “indeterminate” applies where direction or certainty is insufficient. Likelihood does not express the size of a trend. A full-period trend can conceal shorter fluctuations linked to climate patterns, and an upward trend does not mean every year was wetter than the previous one. The release supports environmental monitoring; it does not attribute individual wet or dry years to a single cause.