The pattern of seasonal temperature odds across southeast Australia is a result
of recent warm conditions in the Indian Ocean and an increasing level
of warmth in the Pacific.
The chance that the average July-September maximum temperature will exceed the
long-term median maximum temperature is around 60 to 70% for most of NSW (excluding the
southern border region) and South Australia (excluding the south and southeastern region).
This means that for every ten years with ocean patterns like the current, about six
or seven years would be expected to be warmer than average during the September
quarter over this broad zone, with about three or four years being cooler.
For the remainder of southeast Australia, including the southern border
region of NSW and southeastern region of SA, the chances of above average
maximum temperatures are between 50 to 60%.
Outlook confidence is related to how consistently the Pacific and Indian
Oceans affect Australian temperatures. During July to September, history
shows this effect on maximum temperatures to be moderately consistent over the
northeastern half of NSW, northern SA and north coast of Tasmania (see background information).
However, the effect is weak to very weak in the southeast and southwest of
SA, southwest NSW, most of Victoria and central southern Tasmania. In areas
where outlook confidence is not high, caution should be used when interpreting
The outlook for mean minimum temperatures over July-September shows the
chance of a seasonal average above the long-term median minimum temperature is between
45 and 60% over southeastern Australia.
History shows the oceans' effect on minimum temperatures in the July to
September period to be moderately consistent over parts of northern and
eastern NSW. However, over western NSW, most of SA,
Victoria and Tasmania, the influence is only weakly or very weakly consistent.