June 2025 the wettest June on record in Blenheim

Monday, 7 July 2025

June 2025 has gone down as the wettest June ever recorded in Blenheim, and the second wettest month overall in 96 years of data collection.

According to a weather summary from the Blenheim meteorological station, 191.8 millimetres of rain fell during the month – nearly three times the long-term average of 65mm. Only July 2022 recorded more rainfall, with 220.6mm.

There were two significant rain events last month: 40mm fell on June 5, while a staggering 129.8mm fell between June 26 and 29, contributing to widespread flooding across Marlborough.

Despite no single day exceeding the 100mm threshold used by NIWA to classify a “heavy rain event”, the cumulative volume was enough to push river levels dangerously high. The Awatere River peaked at 533 cubic metres per second on June 27 – exceeding Marlborough District Council’s predicted maximum for a one-in-100-year flood. The Wairau River also surged, reaching 3770m³ per second at Barnetts Bank, just below its maximum floodway capacity.

The month was also marked by low sunshine – with just 139.4 hours recorded, 93% of the long-term average – and a brief but sharp cold snap mid-month. There were seven ground frosts and one air frost.

June’s mean temperature of 9.3C was 0.5C above average, and warmer than the same month in 2022 and 2024.

The rainfall brought the total for the first half of 2025 to 428mm – 142% of the long-term average – making it a stark contrast to the previous year, which recorded just 208.8mm for the same period.

The 12-month hydrological year from July 2024 to June 2025 ended with 724.8mm of rain, also above average.