The Bureau of Meteorology has raised its El Nino-Southern Oscillation Outlook status to La Nina WATCH.
La Nina status could mean an earlier wet season, cooler daytime temperatures, more cyclones and a greater chance of widespread flooding.
BOM meteorologist Peter Markworth said while the event was not a certainty, Scenic Rim, Logan and Redlands were likely to get wet in the coming months.
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"It's looking like an enhanced chance of more rain in July to September with a 65 to 70 percent above average chance of rain during this time period," he said.
"This could increase in the October to July period.
"La Nina hasn't yet occurred but it does look like it will."
The last time La Nina made a big impact on Australia was in 2010 to 2012, triggering the country's wettest two-year period and earning 2011 the title of the coldest year on record in a decade.
BOM yesterday announced a 50 per cent chance of La Nina forming in 2020, double the annual likelihood.
Bureau manager of long-range forecasting Dr Andrew Watkins said changes in the surface temperature of the tropical Pacific Ocean indicated a rise in the chance of a La Nina event this year.
"Tropical Pacific Ocean surface temperatures have cooled in recent weeks, and models suggest this cooling will continue through winter and into spring," Dr Watkins said.
"Temperatures in the top 150 metres of the tropical Pacific are also cooler than average. This means that the surface cooling is not likely to disappear quickly.
"This cooler ocean joining forces with the atmosphere is the cause of changes in global weather patterns."
"Other indicators of La Nina, such as stronger trade winds and lower air pressure over Australia compared with the central Pacific, have yet to appear. Once we start to see a change in these weather patterns, the likelihood of a La Nina event will increase much more. And it also increases the chance of a wetter second half of the year for Australia."
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