9:00pm 09/08/2026 to 9:00pm 11/08/2026
Maximum observed rainfall by duration, estimated return period and AEP
Duration
Rainfall
Start
End
Years
AEP
15m
2.4 mm
1:30am 10/08/2026
1:45am 10/08/2026
1 in 1 years
100.0 %
30m
4.6 mm
1:15am 10/08/2026
1:45am 10/08/2026
1 in 1 years
100.0 %
45m
6.4 mm
1:00am 10/08/2026
1:45am 10/08/2026
1 in 1 years
100.0 %
60m
8.2 mm
1:00am 10/08/2026
2:00am 10/08/2026
1 in 1 years
100.0 %
90m
11.2 mm
12:45am 10/08/2026
2:15am 10/08/2026
1 in 1.0 years
99.9 %
120m
13.6 mm
12:15am 10/08/2026
2:15am 10/08/2026
1 in 1.0 years
99.75 %
3h
17.2 mm
11:15pm 09/08/2026
2:15am 10/08/2026
1 in 1.0 years
99.33 %
4h
26.8 mm
9:15pm 09/08/2026
1:45am 10/08/2026
1 in 1.1 years
91.5 %
6h
33.0 mm
9:15pm 09/08/2026
3:15am 10/08/2026
1 in 1.1 years
87.7 %
9h
39.2 mm
9:15pm 09/08/2026
6:15am 10/08/2026
1 in 1.1 years
91.3 %
12h
39.2 mm
9:15pm 09/08/2026
9:15am 10/08/2026
1 in 1.0 years
98.19 %
18h
41.2 mm
9:15pm 09/08/2026
3:15pm 10/08/2026
1 in 1.0 years
99.68 %
24h
42.2 mm
9:15pm 09/08/2026
9:15pm 10/08/2026
1 in 1.0 years
99.99 %
30h
49.0 mm
9:15pm 09/08/2026
3:15am 11/08/2026
1 in 1.0 years
99.89 %
36h
52.2 mm
9:15pm 09/08/2026
9:15am 11/08/2026
1 in 1.0 years
99.92 %
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.

