1:30pm 24/08/2026 to 1:30pm 26/08/2026
Maximum observed rainfall by duration, estimated return period and AEP
Duration
Rainfall
Start
End
Years
AEP
15m
10.2 mm
11:45pm 25/08/2026
12:00am 26/08/2026
1 in 1.4 years
70.0 %
30m
15.2 mm
11:30pm 25/08/2026
12:00am 26/08/2026
1 in 1.8 years
54.23 %
45m
17.0 mm
11:30pm 25/08/2026
12:15am 26/08/2026
1 in 1.7 years
58.86 %
60m
18.0 mm
11:15pm 25/08/2026
12:15am 26/08/2026
1 in 1.5 years
64.88 %
90m
19.6 mm
10:30pm 25/08/2026
12:00am 26/08/2026
1 in 1.4 years
70.67 %
120m
27.0 mm
10:15pm 25/08/2026
12:15am 26/08/2026
1 in 2.3 years
43.84 %
3h
28.4 mm
9:15pm 25/08/2026
12:15am 26/08/2026
1 in 1.9 years
53.93 %
4h
28.4 mm
7:45pm 25/08/2026
12:15am 26/08/2026
1 in 1.4 years
71.3 %
6h
28.4 mm
6:15pm 25/08/2026
12:15am 26/08/2026
1 in 1.2 years
83.51 %
9h
29.6 mm
10:15pm 25/08/2026
7:15am 26/08/2026
1 in 1.1 years
91.28 %
12h
44.0 mm
10:00pm 25/08/2026
10:00am 26/08/2026
1 in 1.7 years
59.24 %
18h
53.0 mm
6:15pm 25/08/2026
12:15pm 26/08/2026
1 in 1.9 years
52.55 %
24h
53.2 mm
12:15pm 25/08/2026
12:15pm 26/08/2026
1 in 1.5 years
64.55 %
30h
53.2 mm
6:15am 25/08/2026
12:15pm 26/08/2026
1 in 1.4 years
72.38 %
36h
53.2 mm
12:15am 25/08/2026
12:15pm 26/08/2026
1 in 1.3 years
79.54 %
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.

