precipitation · Australia
Perth, Western Australia
May–September rainfall total
Modelled demonstration series · not observed data
Look at the trend line rather than the anomaly on this one. This is not a place having a dry year, it is a place whose rainfall has stepped down and stayed down for decades. Perth's response was to stop relying on rain altogether: the city now takes a large share of its drinking water from desalination.
75 years, modelled
Same reading, two normals
| Normal | Mean | σ | Pct | Return |
|---|---|---|---|---|
| 1951–1980 | 690 mm | −3.10σ | 0.097th | 1 in 1,000 years |
| 1991–2020 | 564 mm | −2.64σ | 0.41th | 1 in 240 years |
Today would be the lowest value in the entire 75-year modelled series. Past the series' standing low of 390 mm (2024). Nothing about the reading changes between rows — only the yardstick.
The season here
South-west Western Australia has one of the clearest long-term drying signals anywhere — the winter storm track has shifted south, away from the coast.
Where this series comes from
MODELLED SERIES — not observed. Parameters set from published south-west Western Australia winter-rainfall climatology and its well-documented multi-decadal decline; lognormal transform applied. The 75 annual values are synthesised by the seeded generator.
Every number on this page comes from a modelled series: 75 annual values synthesised by a seeded generator from published climatological parameters for Perth, Western Australia. It shows how anomaly reasoning works. It is not a measurement and must not be cited as one.
How to read σ
σ counts standard deviations from this place's own normal. The sigma guide · return periods.
More precipitation stations
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