Perth's winter rainfall decline and what to plant now

South-west Western Australia's drying is one of the best-documented regional rainfall shifts anywhere. Peer-reviewed hydrology puts the reduction at 15–20% since the 1970s, with streams shifting from perennial to ephemeral; the Water Corporation states Perth's average annual rainfall has fallen around 20% since the 1970s.

Runoff has fallen much faster than rainfall. Before 1975, Perth's dams received an average of 420 billion litres of streamflow a year. Between 2010 and 2018 that averaged 72.5 billion litres, and in 2015 it hit a record low of 15.8 billion litres — the lowest since records began in 1911.

The rainfall figures depend on the station and period: the Perth Metro station averages 718.5 mm across 1993–2026, against a long-term 1876–2016 historical average of 844.5 mm. We quote both rather than presenting one as the normal.

The Bureau of Meteorology and CSIRO's State of the Climate 2024 projects continued drying in south-west Western Australia, particularly in winter and spring — which is precisely the window in which unirrigated plants establish.

The rules follow the water. WA's permanent water efficiency measures date from 2007, and the winter Sprinkler Switch-off has banned scheme and bore sprinkler use from 1 June to 31 August every year since 2010, saving an estimated five billion litres a year; breaches carry a $100 fine. Since September 2022 garden bore sprinkler rosters in Perth and Mandurah have been two days a week.

For planting, that means autumn planting into a shortening wet window, generous mulch, and locally sourced natives that establish within it. Several Mediterranean species perform well here but a number have naturalised — check Western Australian declarations before buying.