ENSO status: La Niña Watch.
IOD status: Neutral.
SAM status: Negative. Trending slightly negative.

Rainfall outlooks are showing close to average for most of the country during October, with a higher chance of above average rainfall for northern and eastern Australia, increasing further into November and December. Models are also hinting that rainfall is more likely to arrive in the form of showers and thunderstorms, rather than broad rainbands, meaning rainfall in practice will likely be hit-and-miss for most of Australia this spring.

Temperature outlooks are showing above average minimum temperatures across Australia for the next several months. Maximum temperatures are forecast to be above average for WA, SA and the NT, and closer to average in eastern Australia. From November, models show the eastern inland may have cooler daytime temperatures, potentially extending into northern Australia if La Niña develops.

The El Niño Southern Oscillation (ENSO) is in a La Niña Watch, meaning there is approximately a 50% chance of a La Niña developing this year. Overall, models are now starting to look more like La Niña, with more widespread ocean cooling occurring in the South Pacific, helped by the consistently strong trade winds. While these are good signs that La Niña is starting to develop, a declaration would likely happen no earlier than November, meaning this is more likely to be a late and weaker event if it does eventuate. A La Niña typically increases rainfall over northern and southeastern Australia during spring, but has little effect for southwestern WA. It also leads to cooler daytime temperature, but overall warmer nights across northern and eastern Australia during spring. 

The Indian Ocean Dipole (IOD) is in a neutral phase and is now unlikely to develop into either phase this spring. Conditions are closer to a positive IOD than to a negative phase, so there may be some minor reductions in the frequency of northwest cloudbands impacting Australia, increasing daytime temperatures for the inland. A neutral IOD tends to bring a small increase in spring rainfall for southwest WA, but has little effect on rainfall elsewhere or on temperatures.

The Southern Annular Mode (SAM) is in a negative phase, continuing on from the initial sudden Stratospheric Warming (SW) events over Antarctica since mid-July. These events increase the chances of negative SAM events, but are having a lesser effect moving forward in October. A negative SAM increases the frequency of cold fronts. During spring, this increases rainfall over western Tas and southern Vic, but decreases rainfall over eastern Australia. More fronts also increases the frequency of both hot and cold days, with a net effect of warmer than average days. Minimums tend to be much warmer than average through southern Australia.