6:45am 21/08/2026 to 6:45am 23/08/2026
Maximum observed rainfall by duration, estimated return period and AEP
Duration
Rainfall
Start
End
Years
AEP
15m
3.6 mm
10:00am 22/08/2026
10:15am 22/08/2026
1 in 1.0 years
98.54 %
30m
5.2 mm
9:45am 22/08/2026
10:15am 22/08/2026
1 in 1.0 years
97.97 %
45m
7.0 mm
9:30am 22/08/2026
10:15am 22/08/2026
1 in 1.1 years
95.14 %
60m
8.6 mm
9:15am 22/08/2026
10:15am 22/08/2026
1 in 1.1 years
90.8 %
90m
11.8 mm
9:15am 22/08/2026
10:45am 22/08/2026
1 in 1.3 years
79.42 %
120m
12.0 mm
8:45am 22/08/2026
10:45am 22/08/2026
1 in 1.2 years
86.47 %
3h
16.0 mm
7:45am 22/08/2026
10:45am 22/08/2026
1 in 1.4 years
72.36 %
4h
18.0 mm
6:30am 22/08/2026
11:00am 22/08/2026
1 in 1.4 years
72.45 %
6h
18.2 mm
6:00am 22/08/2026
12:00pm 22/08/2026
1 in 1.3 years
78.79 %
9h
18.2 mm
3:00am 22/08/2026
12:00pm 22/08/2026
1 in 1.1 years
87.69 %
12h
18.4 mm
7:15am 22/08/2026
7:15pm 22/08/2026
1 in 1.1 years
90.58 %
18h
19.0 mm
2:00am 22/08/2026
8:00pm 22/08/2026
1 in 1.1 years
93.46 %
24h
19.6 mm
4:00am 22/08/2026
4:00am 23/08/2026
1 in 1.1 years
94.77 %
30h
19.6 mm
10:00pm 21/08/2026
4:00am 23/08/2026
1 in 1.0 years
95.79 %
36h
19.6 mm
4:00pm 21/08/2026
4:00am 23/08/2026
1 in 1.0 years
96.53 %
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.

