Australia is officially in an El Niño event after a La Niña pattern brought three years of cool temperatures and record-breaking rain.
The Bureau of Meteorology (BoM) made the long-awaited announcement today, ending months of speculation.
So what exactly does this mean for Australia's weather, and what is going to happen next? We answer all of your El Niño and La Niña questions.
What is El Niño and how is it different to La Niña?
The cycle of La Niña and El Niño – known as ENSO, or the El Niño-Southern Oscillation index – works a bit like a pendulum.
La Niña occurs when water in the eastern tropical region of the Pacific Ocean is cooler than average as the "trade winds" – the planet's prevailing east-to-west winds – strengthen, creating warmer-than-normal water around Indonesia and Australia's east coast.
This leads to increased rainfall and brings the risk of heavy flooding in Australia.
However, when those conditions are reversed – trade winds are weaker, and water is warmer than average in the eastern tropical Pacific but cooler close to Australia – an El Niño is declared, and our continent will experience hot, dry conditions and come under the threat of drought.
When the "pendulum" sits in the middle and ocean temperatures are closer to average, it is referred to as "neutral" ENSO conditions - and it is more likely to bring less extreme weather conditions.
And, if you're wondering what the two terms actually mean, "La Niña" is Spanish for "the girl" or "little girl", while "El Niño" translates to "the boy" or "little boy".
What is El Niño predicted to bring?
Put simply, the weather event will bring hotter, drier conditions, which will, in turn, increase the likelihood of bushfires.
It is Australia's first El Niño event in about eight years.
The declaration came two months after the United Nations' World Meteorological Organisation had previously declared El Niño's arrival, predicting hot weather and tumbling temperature records.
Conditions for an El Niño event have met the required three of four criteria, the BoM said today.
"Central and eastern Pacific sea surface temperatures continue to exceed El Niño thresholds.
"Models indicate further warming of the central to eastern Pacific is likely.
"Overall, there are signs that the atmosphere is responding to the pattern of sea surface temperatures in the tropical Pacific and coupling of the ocean and atmosphere has started to occur.
"This coupling is a characteristic of an El Niño event and is what strengthens and sustains an event for an extended period."
The BoM's criteria to declare an El Niño include: a sea surface temperature that is 0.8 degrees warmer than average; trade winds that are weaker than average in the western or central equatorial Pacific Ocean during any three of the last four months; and a three-month average Southern Oscillation Index of –7 or lower; and a majority of surveyed climate models show sustained warming to at least 0.8 degrees above average in key Pacific regions.
When was the last time Australia had an El Niño?
Australia's last El Niño event occurred during the summer of 2015-16, while the last time the Bureau declared an El Niño alert was in April 2019.
The country had a severe drought throughout 2019 and the strong El Niño system was partly responsible.
The 2019 drought was measured by the BoM to be Australia's most intense ever recorded.
Fires to floods: Wild weather hits Australia's east-coast
Has La Niña ended in Australia?
Yes, the Bureau officially declared back in March that we'd seen the end of La Niña's seemingly endless drenching.
The announcement marked the end of three back-to-back years of the weather event, which played a major role in the flooding of dozens of communities up and down the nation's east coast.
How long did Australia have La Niña?
La Niña was declared in each of the last three summers, with conditions returning to neutral in between every time.
In most cases, La Niña events will appear for one summer, or sometimes twice in a row.
Last summer's third consecutive event was only the third time since 1950 there has been a "triple-dip" La Niña.
