Autumn weather update

Marlborough was slightly wetter and less windy than usual in autumn 2026.

There were two large rain events in May when northerly storms brought excess rainfall to catchments in northern Marlborough. The rain event at the end of May resulted in a peak flow of 3,000 cubic metres per second (cumecs) in the Wairau River.

Hydrologist Charlotte Tomlinson presented her autumn report to Council’s Environment and Planning meeting, saying autumn rainfall in Blenheim was slightly above average at 173mm. March and May were both dry months with just 50 per cent of average rainfall while in April it was more than twice the monthly average.

Autumn rainfall across the region was average to slightly above average and higher in eastern coastal areas and northern parts of the region due to both easterly and northerly rain events.

Baseflow in the Awatere River has remained elevated since January with no restrictions on water users in autumn. The lowest flow in the Wairau River (11 cumecs) occurred in late March with no class A restrictions on water users during the 2025/26 irrigation season.

El Nino weather conditions were expected to develop during winter which typically means reduced rainfall on the East Coast, Ms Tomlinson said. Winter rainfall was likely to be average or below average.

Temperature-wise, it was a cool start to autumn with March cooler than average but April and May were slightly warmer than average. The average autumn temperature in Blenheim was 13.9 degrees.

There were two ground frosts over autumn; during the past 90 years, autumn frosts in Blenheim have been on the decline.