La Nina has officially been declared to be active in the Pacific Ocean, following several months of 'watch' and 'alert' status, according to the Bureau of Meteorology.
Bureau Climate Operations manager Andrew Watkins said there was warmer water in the Pacific Ocean near the coast of Australia and cooler water closer to South America, which tends to favour more rain and cooler temperatures for the coming months, particularly for central, eastern and northern Australia.
The United States National Oceanic and Atmospheric Administration declared an active La Nia status on September 10.
Dr Watkins said La Nina's typically formed in winter and spring and persisted through to the following autumn, but there were cases of the event persisting for longer, as was the situation in 2010-11, which then persisted into 2012.
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"The last official La Nina the BoM declared was in 2010-11, and we certainly saw some big impacts with it one of the wettest two-year periods on record for Australia," he said.
But he warned the same situation was unlikely to occur this time, with the 2010-12 event one of the strongest La Nina's they had seen, while this was more "moderate".
Dr Watkins did say as well as above average rainfall, La Nina also was linked with increased tropical cyclones and flooding.
He said it would also likely have an impact on the bushfire season, although there would still be bushfires across summer, just likely to be lesser in impact.
Dr Watkins said La Nina was also likely to mean less intense heat waves, such as have been seen in recent years, but those heatwaves that did occur would likely last longer - due to the slower moving weather pattern - and probably be more humid.
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