Climate outlook for December to March

Issued 5 November 2020

Climate outlook overview

December to February rainfall is likely to be above average across most of Australia, except west coast Tasmania.
Daytime temperatures during December to February are likely to be warmer than average across parts of south-east and far-west Australia, as well as along the northern coastline.
Night-time temperatures during December to February are very likely (greater than 80% chance) to be warmer than average across almost all of Australia.
La Niña is underway in the tropical Pacific. La Niña typically increases the likelihood of above average rainfall across much of Australia during spring and early summer.
A positive Southern Annular Mode (SAM) may also enhance rainfall in the east over the coming month.

December to February is likely to be wetter than average for nearly all of Australia (greater than 70% chance in most areas), except western Tasmania where there is increased chance of drier than average conditions. A similar outlook exists for December though the likelihood of above average rainfall is not as high (greater than 60% chance in most areas) with western Victoria, south-east Queensland and north-east WA likely to have roughly equal chances of a wetter or drier than average December.
The fortnight 9-22 November is likely to be wetter than average for south-west WA and northern NT (greater than 75% chance), as well as most of the other parts of the eastern two-thirds of the Australian mainland, especially towards the interior (greater than 60% chance). The northern coast of WA and western Tasmania are more likely to experience drier than average conditions.
While the outlooks indicate wetter than average conditions, southern parts of Australia are entering into their drier season, so rainfall is not likely to be sufficient to relieve long-term rainfall deficits.

For the fortnight 9-22 November, average daytime temperatures are likely to be above the long-term average for north-east WA as well as most of the eastern two-thirds of Australia apart from the NSW coast, where roughly equal chances of warmer or cooler days are more likely. Average daytime temperatures are likely to be below the long-term average for south-west WA and along the Ningaloo Coast. On average, nights during this period are likely to be warmer than the long-term average across almost all of Australia.
The average maximum temperature for December to February is likely to be higher than the long-term average for Victoria, Tasmania, the far west of WA, the northern coastlines of NT and Queensland, and parts of eastern SA, southern Queensland and western NSW. However, it is likely to be cooler than the long-term average for south coast WA, north-east WA, and north-west NT.
The average minimum temperature is very likely (greater than 80% chance) to be higher than the long-term average across Australia during December to February, apart from around south-east WA where there is a closer to 60% chance.

The Bureau's ENSO Outlook is at La Niña, meaning La Niña is underway in the tropical Pacific Ocean.
Model outlooks suggest the La Niña is likely to persist until at least the end of the 2020-21 Australian summer.
The Indian Ocean Dipole (IOD) is neutral. The majority of models indicate that the IOD will remain neutral over the coming months.
Waters to the north of Australia have warmed over the past month, which may also enhance rainfall over the continent.
The Southern Annular Mode (SAM) is expected to be positive in the coming weeks, with generally positive values expected over the 2020-21 summer. This typically enhances the wet signal of La Niña in parts of eastern Australia, although western Tasmania is often drier.
Australia's temperature and rainfall variability are also influenced by global warming caused by human activities. Australia's climate has warmed by around 1.4 °C since 1910, while southern Australia has seen a reduction of 10–20% in cool season (April–October) rainfall in recent decades.

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