1:10pm 05/08/2026 to 1:10pm 07/08/2026
Maximum observed rainfall by duration, estimated return period and AEP
Duration
Rainfall
Start
End
Years
AEP
10m
5.4 mm
11:00am 07/08/2026
11:10am 07/08/2026
1 in 1.1 years
94.57 %
20m
9.2 mm
11:00am 07/08/2026
11:20am 07/08/2026
1 in 1.3 years
78.54 %
30m
11.8 mm
10:50am 07/08/2026
11:20am 07/08/2026
1 in 1.4 years
69.9 %
60m
12.0 mm
10:20am 07/08/2026
11:20am 07/08/2026
1 in 1.1 years
90.96 %
90m
12.0 mm
9:50am 07/08/2026
11:20am 07/08/2026
1 in 1.0 years
96.99 %
120m
12.0 mm
9:20am 07/08/2026
11:20am 07/08/2026
1 in 1.0 years
98.66 %
3h
12.0 mm
8:20am 07/08/2026
11:20am 07/08/2026
1 in 1.0 years
99.77 %
4h
14.6 mm
7:00am 07/08/2026
11:30am 07/08/2026
1 in 1.0 years
99.33 %
6h
14.6 mm
7:00am 07/08/2026
1:00pm 07/08/2026
1 in 1.0 years
99.84 %
9h
17.2 mm
2:20am 07/08/2026
11:20am 07/08/2026
1 in 1.0 years
99.75 %
12h
19.6 mm
11:20pm 06/08/2026
11:20am 07/08/2026
1 in 1.0 years
99.4 %
18h
19.6 mm
5:20pm 06/08/2026
11:20am 07/08/2026
1 in 1.0 years
99.9 %
24h
19.6 mm
11:20am 06/08/2026
11:20am 07/08/2026
1 in 1 years
100.0 %
30h
19.6 mm
5:20am 06/08/2026
11:20am 07/08/2026
1 in 1 years
100.0 %
36h
19.6 mm
11:20pm 05/08/2026
11:20am 07/08/2026
1 in 1 years
100.0 %
48h
19.6 mm
1:10pm 05/08/2026
1:10pm 07/08/2026
1 in 1 years
100.0 %
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.

