3:30am 18/07/2026 to 3:30am 20/07/2026
Maximum observed rainfall by duration, estimated return period and AEP
Duration
Rainfall
Start
End
Years
AEP
15m
2.0 mm
7:15pm 18/07/2026
7:30pm 18/07/2026
1 in 1 years
100.0 %
30m
4.0 mm
2:30pm 19/07/2026
3:00pm 19/07/2026
1 in 1 years
100.0 %
45m
4.0 mm
7:15pm 18/07/2026
8:00pm 18/07/2026
1 in 1 years
100.0 %
60m
6.0 mm
7:15pm 18/07/2026
8:15pm 18/07/2026
1 in 1 years
100.0 %
90m
8.0 mm
7:15pm 18/07/2026
8:45pm 18/07/2026
1 in 1 years
100.0 %
120m
10.0 mm
7:15pm 18/07/2026
9:15pm 18/07/2026
1 in 1 years
100.0 %
3h
13.0 mm
6:15pm 18/07/2026
9:15pm 18/07/2026
1 in 1 years
100.0 %
4h
18.0 mm
4:30pm 18/07/2026
9:00pm 18/07/2026
1 in 1 years
100.0 %
6h
23.0 mm
7:15pm 18/07/2026
1:15am 19/07/2026
1 in 1.0 years
99.81 %
9h
34.0 mm
6:15pm 18/07/2026
3:15am 19/07/2026
1 in 1.0 years
98.27 %
12h
43.0 mm
4:30pm 18/07/2026
4:30am 19/07/2026
1 in 1.0 years
95.61 %
18h
55.0 mm
3:30pm 18/07/2026
9:30am 19/07/2026
1 in 1.1 years
91.87 %
24h
69.0 mm
4:00pm 18/07/2026
4:00pm 19/07/2026
1 in 1.2 years
86.65 %
30h
81.0 mm
4:00pm 18/07/2026
10:00pm 19/07/2026
1 in 1.2 years
80.08 %
36h
86.0 mm
2:00pm 18/07/2026
2:00am 20/07/2026
1 in 1.2 years
80.75 %
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.

