1:45pm 25/08/2026 to 1:45pm 27/08/2026
Maximum observed rainfall by duration, estimated return period and AEP
Duration
Rainfall
Start
End
Years
AEP
15m
2.2 mm
9:30am 27/08/2026
9:45am 27/08/2026
1 in 1 years
100.0 %
30m
4.0 mm
9:30am 27/08/2026
10:00am 27/08/2026
1 in 1.0 years
99.8 %
45m
5.2 mm
9:15am 27/08/2026
10:00am 27/08/2026
1 in 1.0 years
99.22 %
60m
6.8 mm
9:00am 27/08/2026
10:00am 27/08/2026
1 in 1.0 years
97.82 %
90m
9.2 mm
9:00am 27/08/2026
10:30am 27/08/2026
1 in 1.1 years
93.48 %
120m
10.6 mm
8:30am 27/08/2026
10:30am 27/08/2026
1 in 1.1 years
91.6 %
3h
15.0 mm
9:00am 27/08/2026
12:00pm 27/08/2026
1 in 1.3 years
76.96 %
4h
19.4 mm
8:30am 27/08/2026
1:00pm 27/08/2026
1 in 1.5 years
67.03 %
6h
23.0 mm
7:00am 27/08/2026
1:00pm 27/08/2026
1 in 1.7 years
60.58 %
9h
26.2 mm
4:30am 27/08/2026
1:30pm 27/08/2026
1 in 1.7 years
60.44 %
12h
29.2 mm
1:30am 27/08/2026
1:30pm 27/08/2026
1 in 1.7 years
57.51 %
18h
30.2 mm
7:30pm 26/08/2026
1:30pm 27/08/2026
1 in 1.5 years
64.87 %
24h
30.2 mm
1:30pm 26/08/2026
1:30pm 27/08/2026
1 in 1.4 years
69.76 %
30h
30.2 mm
7:30am 26/08/2026
1:30pm 27/08/2026
1 in 1.4 years
73.4 %
36h
30.2 mm
1:30am 26/08/2026
1:30pm 27/08/2026
1 in 1.3 years
76.16 %
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.

