The Bureau of Meteorology has declared that a moderate strength La Nina has developed in the Pacific Ocean.
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It's upgraded its alert to an active event.
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La Nina typically results in above-average spring rainfall for Australia, particularly across eastern, central and northern regions.
The last La Nia event occurred from 2010-2012 and resulted in one of Australia's wettest two-year periods on record, including the 2011 floods in Horsham.
The bureau's Dr Andrew Watkins said southeastern Australia typically received more rain in Spring and Summer during a La Nina event.
"This can wet up the soils and make the chance of widespread and flash flooding higher," he said. "It also means more water going into our storages, which is a good thing in many areas.
"It also reduces the risk of fires and extreme heat waves, but the ones we do get tend to be longer and more humid."
Last week, the bureau predicted flash flooding for Halls Gap and Glenorchy.
Dr Watkins said southeastern Australia would still see summer bushfires during a La Nina event.
It can also mean cooler days, more tropical cyclones, and an earlier onset of the first rains of the wet season across the north.
The bureau said that recent changes in ocean temperatures and weather patterns over the Pacific were now likely to remain until at least the end of the year.
La Nina is the cool phase of the El Nino Southern Oscillation.
It is associated with cooler than average sea surface temperatures (SSTs) in the central and eastern tropical Pacific Ocean.
La Nina events often form in autumn or winter, then decay in late summer.
The greatest impact normally occurs during the spring and early summer period.
La Nina events normally last for around a year, however they can be shorter, or much longer.
Recent observations and model forecasts show the central tropical Pacific Ocean is now 0.8°C cooler than normal, and that has resulted in changes to trade winds and pressure patterns.
Climate models suggest these patterns will continue until at least the end of the year.
The last La Nina event occurred from 2010-2012 and resulted in one of Australia's wettest two-year periods on record.
Widespread flooding occurred in many parts of Australia associated with the record rainfalls.
Tropical cyclone activity in the 2010-2011 season was near normal.
However, five of the tropical cyclones during 2010-11 were in the severe category, which is above average, including Tropical Cyclone Yasi, which caused widespread damage to far north Queensland.
The impacts of La Nina can vary significantly between events.
It is likely this year will not see the same intensity as the 2010-11 La Nina event, but is still likely to be of moderate strength.
The Bureau previously shifted from La Nina WATCH to La Nina ALERT on 18 August 2020.
The US National Oceanic and Atmospheric Administration declared an active La Nina status on September 10, 2020.
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Alexander Darling
Alexander has been a member of the Wimmera Mail-Times' editorial team since December 2018, covering politics, business and property among other rounds. He is a passionate St.Kilda and rock and roll fan, and has previously worked as a radio reporter in Port Macquarie and Gosford, NSW.
Alexander has been a member of the Wimmera Mail-Times' editorial team since December 2018, covering politics, business and property among other rounds. He is a passionate St.Kilda and rock and roll fan, and has previously worked as a radio reporter in Port Macquarie and Gosford, NSW.
Andrew Miller
I'm a general reporter with Stock & Land, with a special interest in irrigation issues. I completed my cadetship, with the Age, in 1980. Over my career, I've worked for ABC radio news (Mt Isa, Qld) and at provincial and suburban newspapers.
I'm a general reporter with Stock & Land, with a special interest in irrigation issues. I completed my cadetship, with the Age, in 1980. Over my career, I've worked for ABC radio news (Mt Isa, Qld) and at provincial and suburban newspapers.
