5:00am 30/07/2026 to 5:00am 01/08/2026
Maximum observed rainfall by duration, estimated return period and AEP
Duration
Rainfall
Start
End
Years
AEP
15m
9.6 mm
12:15pm 31/07/2026
12:30pm 31/07/2026
1 in 1.1 years
90.79 %
30m
12.6 mm
12:00pm 31/07/2026
12:30pm 31/07/2026
1 in 1.1 years
90.25 %
45m
13.4 mm
12:00pm 31/07/2026
12:45pm 31/07/2026
1 in 1.0 years
95.25 %
60m
13.4 mm
11:45am 31/07/2026
12:45pm 31/07/2026
1 in 1.0 years
98.17 %
90m
14.2 mm
12:00pm 31/07/2026
1:30pm 31/07/2026
1 in 1.0 years
98.89 %
120m
16.6 mm
10:45am 31/07/2026
12:45pm 31/07/2026
1 in 1.0 years
98.28 %
3h
23.0 mm
9:30am 31/07/2026
12:30pm 31/07/2026
1 in 1.1 years
89.94 %
4h
25.0 mm
9:30am 31/07/2026
2:00pm 31/07/2026
1 in 1.1 years
93.37 %
6h
26.6 mm
7:30am 31/07/2026
1:30pm 31/07/2026
1 in 1.0 years
95.24 %
9h
34.2 mm
7:15am 31/07/2026
4:15pm 31/07/2026
1 in 1.1 years
87.88 %
12h
36.2 mm
6:15am 31/07/2026
6:15pm 31/07/2026
1 in 1.1 years
90.23 %
18h
37.2 mm
2:00am 31/07/2026
8:00pm 31/07/2026
1 in 1.0 years
95.89 %
24h
37.6 mm
4:00am 31/07/2026
4:00am 01/08/2026
1 in 1.0 years
98.19 %
30h
37.6 mm
10:00pm 30/07/2026
4:00am 01/08/2026
1 in 1.0 years
98.83 %
36h
37.6 mm
4:00pm 30/07/2026
4:00am 01/08/2026
1 in 1.0 years
99.38 %
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.

