On the other hand, the odds are shifted in favour of a wetter than normal season in southwest WA.

The pattern of seasonal rainfall odds across Australia is a result of recent warm conditions in the Indian Ocean and warming in the Pacific, according to the Bureau of Meteorology.

The forecast comes despite the sharp upturn in the southern Oscillation Index (SOI).

The SOI 30-day moving average reached +11 this week, after dipping into negative figures during June.

The Pacific influence, however, dominates the outlook in eastern Australia, according to the bureau, while the Indian Ocean has had a greater influence on the probabilities in WA.

For the August to October period, the chance of exceeding median rainfall is below 40pc in a broad area extending over most of Queensland, the far east of the NT, the eastern half of SA, far western NSW, the western half of Victoria and into northern Tasmania (see map).

Within this zone, the chances drop to around 20pc in north-central Queensland. This means that for every 10 years with ocean patterns like the current, about two to four years would be expected to be wetter than average in these parts of eastern Australia during this three-month period, with about six to eight being drier.

In contrast, over southwest WA the chances of exceeding the seasonal median rainfall are between 60-65pc.

Over most remaining parts of the country, the chance of a wetter than average season is between 40-50pc. In other words, the chances of above normal falls are about the same as the chances of below normal.

Despite the current upturn in the SOI, the bureau says, an El Niño event looks to be developing across the Pacific.

The latest outputs from computer models indicate it will reach peak intensity late in the year.

El Niño events are usually (but not always) associated with below normal rainfall in the second half of the year across large parts of southern and inland eastern Australia.