Great Southern
On 14 March 2025 the Bureau of Meteorology’s Albany station recorded 126.4 millimetres in twenty-four hours. That is the highest daily rainfall in a record that began in 1877, beating the previous all-time figure of 113.6 millimetres set on 21 November 2008 and dwarfing the previous March record of 89.7 millimetres from 1917. Albany’s total for the month reached 145.2 millimetres, 382 per cent of its March average. The event triggered a natural disaster declaration for the City of Albany and the Shire of Plantagenet. Its engineering significance is not the daily total, though — it is the intensity underneath it.
What happened
A cloud band brought showers and thunderstorms down over the south-west, with daily rainfall in excess of 30 millimetres widely and totals of 100 to 150 millimetres on the 14th. The storm began in the late afternoon of Thursday 13 March and ran into Friday morning. The worst-affected corridor ran from the Porongurups to Cranbrook and down through Mount Barker to Albany.
Mount Barker recorded 80.4 millimetres on the day at the Bureau’s station, against a previous March record of 57.4 millimetres set in 1956 over a 138-year record. Albany Airport recorded 107.8 millimetres for the month — its highest March total on record. State Emergency Service volunteers took around 150 calls for assistance across the Great Southern. Schools and childcare centres closed, roads flooded, and a Rex flight was diverted to Perth.
The event was declared under the disaster recovery funding arrangements as AGRN 1208, covering storms and associated flooding in the Great Southern on 13 and 14 March 2025, with the City of Albany and the Shire of Plantagenet named as the affected local governments.
The number that matters is not 126.4
A daily total is a poor description of an event like this. The Bureau’s own commentary was more useful: many places recorded in the region of 30 millimetres in half an hour to an hour. A forecaster put the mechanism plainly — a thunderstorm delivering 50 millimetres over Albany would be unusual on its own, but it was the continuation over several hours that tipped it into record territory.
Thirty millimetres in half an hour is a short-duration intensity, and short-duration intensity is what governs urban drainage, culvert sizing, road crossing capacity and overland flow paths. A twenty-four hour total governs almost none of those things. Designing against a daily depth and reporting compliance against it is a common way to produce a system that satisfies the report and fails the storm.
Why the warning system did not help
The Bureau’s flood forecasting and warning service for Western Australia is scoped, in its own service level specification, to riverine flooding caused by rainfall where typical rain-to-flood times are six hours or more. On the south coast the coverage thins from there: the Denmark River has information locations but no forecast service, and the Kent, the Frankland and the wider Albany Coast are data collection only. The Bremer, Hay, Kalgan and King catchments are not in the document’s schedules at all.
A 30 millimetre half-hour burst over an urban catchment is not a six-hour riverine problem. It sits outside the warning service by design, and outside the floodplain mapping by scope — DWER’s mapping addresses major river flooding only, and expressly not stormwater drainage. The region that set an all-time daily rainfall record in 2025 has neither quantitative flood forecasting on its major rivers nor published stormwater flood mapping for the mechanism that actually put water on the ground.
What to take from it, and what not to
One thing to resist: a single record does not re-derive a design rainfall. Australian Rainfall and Runoff intensity-frequency-duration estimates are built from long station records, and one extreme observation shifts them very little. Nor has any official attribution been published linking the March 2025 event to climate change or to a revision of design rainfall. Anyone claiming either is going beyond the record.
What is legitimate is narrower and more useful. The event is a real, local, well-documented calibration point for short-duration storm behaviour in a region where such points are scarce. It demonstrates that the Great Southern’s exposure is short-duration and stormwater-led rather than slow riverine. And it is a reminder that the standard defence — "the mapping does not show flooding here" — describes what has been mapped rather than what can happen.
For a specific site the practical question is unchanged and is answerable: what does a 30 millimetre half-hour burst do to the overland flow path across this land, and does the drainage that exists have anywhere to put it.