4:15am 31/08/2026 to 4:15am 02/09/2026
Maximum observed rainfall by duration, estimated return period and AEP
Duration
Rainfall
Start
End
Years
AEP
15m
2.2 mm
8:15pm 01/09/2026
8:30pm 01/09/2026
1 in 1 years
100.0 %
30m
4.0 mm
8:00pm 01/09/2026
8:30pm 01/09/2026
1 in 1 years
100.0 %
45m
4.6 mm
6:00pm 01/09/2026
6:45pm 01/09/2026
1 in 1 years
100.0 %
60m
6.2 mm
6:00pm 01/09/2026
7:00pm 01/09/2026
1 in 1 years
100.0 %
90m
8.6 mm
5:00pm 01/09/2026
6:30pm 01/09/2026
1 in 1 years
100.0 %
120m
11.4 mm
5:15pm 01/09/2026
7:15pm 01/09/2026
1 in 1.0 years
99.47 %
3h
15.8 mm
4:15pm 01/09/2026
7:15pm 01/09/2026
1 in 1.0 years
97.28 %
4h
22.6 mm
4:00pm 01/09/2026
8:30pm 01/09/2026
1 in 1.1 years
87.25 %
6h
25.6 mm
2:45pm 01/09/2026
8:45pm 01/09/2026
1 in 1.1 years
90.73 %
9h
27.2 mm
1:15pm 01/09/2026
10:15pm 01/09/2026
1 in 1.0 years
98.8 %
12h
27.6 mm
11:45am 01/09/2026
11:45pm 01/09/2026
1 in 1.0 years
99.99 %
18h
27.6 mm
5:45am 01/09/2026
11:45pm 01/09/2026
1 in 1 years
100.0 %
24h
27.6 mm
11:45pm 31/08/2026
11:45pm 01/09/2026
1 in 1 years
100.0 %
30h
27.6 mm
5:45pm 31/08/2026
11:45pm 01/09/2026
1 in 1 years
100.0 %
36h
27.6 mm
11:45am 31/08/2026
11:45pm 01/09/2026
1 in 1 years
100.0 %
Note: A '1 in 1.0 years' estimate means that it is almost certain to occur at least once in a year, and could occur much more than once per year on average. For smaller values like this the Annual Recurrance Interval (ARI) may be of more relevance, but it is complex to calculate for common events.
IFD describes how rainfall intensity relates to how long it lasts and how often it happens. It is the basis for design rainfall used in engineering and flood studies.
- Duration: the length of the rainfall burst, from a few minutes to several days.
- AEP (Annual Exceedance Probability): the chance, in any one year, of a rainfall of that depth or greater. A 1% AEP event has a 1 in 100 chance each year - what is often loosely called a '1 in 100 year' event.
- The curves show design rainfall depths for a range of AEPs. The observed maximums for this location and period are plotted against them so you can see how rare the event was.
Design rainfall data is sourced from the Bureau of Meteorology.

