HowOften? Uncovering meaning in rainfall records. 

 HowOften? Download
To download rainfall data click the State name: QLD, NSW, VIC, WA
To download station data, click here : Data drill
To download the HOWOFTEN manual, click here :


Developed by:

David Freebairn and Stephen Glanville

What is

HowOften? is a WINDOWS program that explores long-term rainfall records to find how frequently rainfall events occur. Some examples of applications include finding:

  • How often planting opportunities occur
  • If there were more wet harvests in the 1950's
  • Seasonal rainfall fluctuations and value of SOI
  • Comparisons between districts
  • Risk associated with opportunity cropping

HowOften? does not predict the weather. It simply looks at what has happened in the past. The user is not restricted to whole months when defining the search period.
Click for case studies.

Using HowOften?

To run the program, simply follow the menu prompts and choose a location, a range of years, a period of time in the year (from 1 to 365 days) and a rainfall specification.
For instance, you may ask: How often between 1920 and 1980 was a planting rain of more than 50mm received at Dalby over a 5 day period from May 16th to July 1st.
HowOften? presents the results as a graph of "wet" years (which meets or exceeds the criteria of your query) and "dry"years (figure 1) or as a daily rainfall calendar(figure 2).

The results may also be compared to the monthly Southern Oscillation Index (SOI) phases.

Inputs for HowOften?

HowOften? uses files of daily rainfall records collected from recording stations all over Australia. Several locations are packaged with the program. More are available by request.
A template is included for entering your own rainfall into HowOften?.

Figure 1.
Graphical output from HowOften?.
  Figure 2.
A rainfall calendar from HowOften?.

Note: The data for some of these locations was synthetically produced where real data were missing.
Disclaimer: While every care is taken, no guarantee of the quality of the rainfall data is given. The raw data remains under copyright.
Extra sites may be produced on request. Email Graeme Wockner

Other Resources

Browse a range of climate products on the internet at the Long Paddock site:

A very comprehensive rainfall software package is Australian Rainman.
The package enables you to:

  • examine historical rainfall records
  • forecast chances of seasonal rainfall
  • identify climatic risks and opportunities
  • study the effects of SOI and SST on rainfall.

It contains tables, graphs and maps and options to enter your own rainfall.
Over 3500 Australian locations are available with temperature, humidity and evaporation data.
Visit the Australian Rainman Internet site on: