9:40pm 18/08/2026 to 9:40pm 20/08/2026
Maximum observed rainfall by duration, estimated return period and AEP
Duration
Rainfall
Start
End
Years
AEP
10m
2.2 mm
6:30am 20/08/2026
6:40am 20/08/2026
1 in 1 years
100.0 %
20m
3.8 mm
6:20am 20/08/2026
6:40am 20/08/2026
1 in 1 years
100.0 %
30m
4.4 mm
2:10am 20/08/2026
2:40am 20/08/2026
1 in 1 years
100.0 %
60m
7.0 mm
2:10am 20/08/2026
3:10am 20/08/2026
1 in 1 years
100.0 %
90m
9.4 mm
2:00am 20/08/2026
3:30am 20/08/2026
1 in 1 years
100.0 %
120m
11.2 mm
5:10pm 19/08/2026
7:10pm 19/08/2026
1 in 1 years
100.0 %
3h
15.8 mm
4:50pm 19/08/2026
7:50pm 19/08/2026
1 in 1.0 years
99.98 %
4h
20.2 mm
4:00pm 19/08/2026
8:30pm 19/08/2026
1 in 1.0 years
99.89 %
6h
21.6 mm
3:10pm 19/08/2026
9:10pm 19/08/2026
1 in 1 years
100.0 %
9h
22.6 mm
3:30pm 19/08/2026
12:30am 20/08/2026
1 in 1 years
100.0 %
12h
32.6 mm
3:40pm 19/08/2026
3:40am 20/08/2026
1 in 1.0 years
99.93 %
18h
38.6 mm
3:30pm 19/08/2026
9:30am 20/08/2026
1 in 1.0 years
99.99 %
24h
49.6 mm
3:50pm 19/08/2026
3:50pm 20/08/2026
1 in 1.0 years
99.6 %
30h
58.4 mm
3:30pm 19/08/2026
9:30pm 20/08/2026
1 in 1.0 years
98.93 %
36h
58.4 mm
9:40am 19/08/2026
9:40pm 20/08/2026
1 in 1.0 years
99.61 %
48h
58.4 mm
9:40pm 18/08/2026
9:40pm 20/08/2026
1 in 1.0 years
99.95 %
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.

