8:00am 22/08/2026 to 8:00am 24/08/2026
Maximum observed rainfall by duration, estimated return period and AEP
Duration
Rainfall
Start
End
Years
AEP
15m
7.0 mm
1:30pm 22/08/2026
1:45pm 22/08/2026
1 in 1.3 years
79.67 %
30m
8.0 mm
9:30pm 23/08/2026
10:00pm 23/08/2026
1 in 1.1 years
88.49 %
45m
12.0 mm
9:00pm 23/08/2026
9:45pm 23/08/2026
1 in 1.4 years
72.6 %
60m
14.0 mm
9:30pm 23/08/2026
10:30pm 23/08/2026
1 in 1.5 years
68.89 %
90m
19.0 mm
9:00pm 23/08/2026
10:30pm 23/08/2026
1 in 1.7 years
57.67 %
120m
21.0 mm
8:45pm 23/08/2026
10:45pm 23/08/2026
1 in 1.8 years
56.71 %
3h
25.0 mm
8:45pm 23/08/2026
11:45pm 23/08/2026
1 in 1.9 years
53.45 %
4h
26.0 mm
7:15pm 23/08/2026
11:45pm 23/08/2026
1 in 1.7 years
59.87 %
6h
29.0 mm
9:00pm 23/08/2026
3:00am 24/08/2026
1 in 1.7 years
58.85 %
9h
31.0 mm
6:15pm 23/08/2026
3:15am 24/08/2026
1 in 1.6 years
63.9 %
12h
31.0 mm
3:15pm 23/08/2026
3:15am 24/08/2026
1 in 1.4 years
69.3 %
18h
31.0 mm
9:15am 23/08/2026
3:15am 24/08/2026
1 in 1.3 years
77.32 %
24h
31.0 mm
3:15am 23/08/2026
3:15am 24/08/2026
1 in 1.2 years
83.01 %
30h
31.0 mm
9:15pm 22/08/2026
3:15am 24/08/2026
1 in 1.2 years
86.75 %
36h
34.0 mm
11:45am 22/08/2026
11:45pm 23/08/2026
1 in 1.2 years
83.81 %
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.

