2:45pm 08/08/2026 to 2:45pm 10/08/2026
Maximum observed rainfall by duration, estimated return period and AEP
Duration
Rainfall
Start
End
Years
AEP
15m
20.0 mm
12:00pm 10/08/2026
12:15pm 10/08/2026
1 in 46.9 years
2.13 %
30m
20.0 mm
11:45am 10/08/2026
12:15pm 10/08/2026
1 in 15.4 years
6.5 %
45m
20.0 mm
11:30am 10/08/2026
12:15pm 10/08/2026
1 in 9.7 years
10.33 %
60m
20.0 mm
11:15am 10/08/2026
12:15pm 10/08/2026
1 in 7.4 years
13.51 %
90m
20.2 mm
11:45am 10/08/2026
1:15pm 10/08/2026
1 in 5.1 years
19.51 %
120m
21.2 mm
12:00pm 10/08/2026
2:00pm 10/08/2026
1 in 4.6 years
21.91 %
3h
21.6 mm
11:45am 10/08/2026
2:45pm 10/08/2026
1 in 3.3 years
30.72 %
4h
21.6 mm
10:15am 10/08/2026
2:45pm 10/08/2026
1 in 2.2 years
46.36 %
6h
21.6 mm
8:45am 10/08/2026
2:45pm 10/08/2026
1 in 1.7 years
59.18 %
9h
21.6 mm
5:45am 10/08/2026
2:45pm 10/08/2026
1 in 1.3 years
74.53 %
12h
21.6 mm
2:45am 10/08/2026
2:45pm 10/08/2026
1 in 1.2 years
85.56 %
18h
21.6 mm
8:45pm 09/08/2026
2:45pm 10/08/2026
1 in 1.1 years
93.65 %
24h
24.4 mm
2:00pm 09/08/2026
2:00pm 10/08/2026
1 in 1.1 years
92.84 %
30h
24.8 mm
8:45am 09/08/2026
2:45pm 10/08/2026
1 in 1.0 years
95.36 %
36h
24.8 mm
2:45am 09/08/2026
2:45pm 10/08/2026
1 in 1.0 years
96.61 %
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.

