4:15am 31/08/2026 to 4:15am 02/09/2026
Maximum observed rainfall by duration, estimated return period and AEP
Duration
Rainfall
Start
End
Years
AEP
15m
2.8 mm
4:15pm 01/09/2026
4:30pm 01/09/2026
1 in 1 years
100.0 %
30m
5.2 mm
4:00pm 01/09/2026
4:30pm 01/09/2026
1 in 1 years
100.0 %
45m
7.6 mm
4:15pm 01/09/2026
5:00pm 01/09/2026
1 in 1 years
100.0 %
60m
10.0 mm
4:00pm 01/09/2026
5:00pm 01/09/2026
1 in 1.0 years
98.99 %
90m
13.4 mm
3:45pm 01/09/2026
5:15pm 01/09/2026
1 in 1.0 years
96.73 %
120m
17.0 mm
4:00pm 01/09/2026
6:00pm 01/09/2026
1 in 1.1 years
89.35 %
3h
25.2 mm
3:45pm 01/09/2026
6:45pm 01/09/2026
1 in 1.7 years
59.51 %
4h
33.0 mm
3:15pm 01/09/2026
7:45pm 01/09/2026
1 in 2.0 years
50.47 %
6h
39.0 mm
2:15pm 01/09/2026
8:15pm 01/09/2026
1 in 2.0 years
49.4 %
9h
41.6 mm
1:00pm 01/09/2026
10:00pm 01/09/2026
1 in 1.3 years
75.21 %
12h
42.0 mm
1:00pm 01/09/2026
1:00am 02/09/2026
1 in 1.1 years
94.78 %
18h
42.0 mm
9:45am 01/09/2026
3:45am 02/09/2026
1 in 1.0 years
99.88 %
24h
42.2 mm
3:45am 01/09/2026
3:45am 02/09/2026
1 in 1 years
100.0 %
30h
42.2 mm
9:45pm 31/08/2026
3:45am 02/09/2026
1 in 1 years
100.0 %
36h
42.2 mm
3:30pm 31/08/2026
3:30am 02/09/2026
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.

