8:45pm 23/08/2026 to 8:45pm 25/08/2026
Maximum observed rainfall by duration, estimated return period and AEP
Duration
Rainfall
Start
End
Years
AEP
15m
4.8 mm
5:00pm 25/08/2026
5:15pm 25/08/2026
1 in 1.0 years
98.63 %
30m
6.2 mm
7:30am 25/08/2026
8:00am 25/08/2026
1 in 1.0 years
99.12 %
45m
7.8 mm
7:15am 25/08/2026
8:00am 25/08/2026
1 in 1.0 years
98.67 %
60m
8.6 mm
7:00am 25/08/2026
8:00am 25/08/2026
1 in 1.0 years
98.84 %
90m
10.4 mm
5:00pm 25/08/2026
6:30pm 25/08/2026
1 in 1.0 years
98.63 %
120m
12.0 mm
6:00am 25/08/2026
8:00am 25/08/2026
1 in 1.0 years
98.38 %
3h
15.4 mm
5:00am 25/08/2026
8:00am 25/08/2026
1 in 1.0 years
96.26 %
4h
19.6 mm
3:30am 25/08/2026
8:00am 25/08/2026
1 in 1.1 years
92.45 %
6h
26.2 mm
2:00am 25/08/2026
8:00am 25/08/2026
1 in 1.3 years
76.87 %
9h
32.8 mm
1:45am 25/08/2026
10:45am 25/08/2026
1 in 1.5 years
68.82 %
12h
35.8 mm
1:30am 25/08/2026
1:30pm 25/08/2026
1 in 1.4 years
70.56 %
18h
49.0 mm
12:45am 25/08/2026
6:45pm 25/08/2026
1 in 2.0 years
49.53 %
24h
49.6 mm
8:45pm 24/08/2026
8:45pm 25/08/2026
1 in 1.7 years
59.56 %
30h
49.6 mm
2:45pm 24/08/2026
8:45pm 25/08/2026
1 in 1.5 years
67.34 %
36h
49.6 mm
8:45am 24/08/2026
8:45pm 25/08/2026
1 in 1.4 years
72.66 %
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.

