There is a 60 per cent chance of a weak La Nina event developing during September to November 2020, according to the World Meteorological Organization.
But the organisation warns the La Nina will not prevent 2020 from being one of the warmest years on record.
An El Nino typically has a warming influence on global temperatures, while La Nina has the opposite effect.
"Even if a La Nina event does develop, its cooling signal will not be enough to counterbalance the impact of human-induced climate change," WMO Secretary-General Professor Petteri Taalas said.
"2020 remains on track to be one of the warmest years on record, with much extreme weather ranging from scorching temperatures and wildfires to devastating floods and marine heatwaves.
"This is largely the result of greenhouse gases rather than naturally occurring climate drivers."
Taking into account La Nina and other influences on regional climates, the Global Seasonal Climate Update indicates elevated probabilities of above-normal rainfall across parts of Australia and south and southeast Asia.
Below-normal seasonal rainfall is forecast in the Horn of Africa and Southern Africa and across the western and southeast Pacific, as well as across central North America.
Model predictions and expert opinion indicate a 60pc chance of La Nina development during September-November 2020.
The chance of neutral El Nino/Southern Oscillation conditions continuing is 40pc, while the chance of El Nino is near 0pc.
Chances for La Nina decrease to 55pc for December to February.
The last La Nina was in 2017-18.
It was a short-lived weak-to-moderate event that started developing in November 2017 and decayed in April 2018.
WMO's Global Seasonal Climate Update indicates that sea surface temperatures for September to November are expected to be above average for much of the globe and this will influence land surface temperatures.
"Below-average temperature is generally unlikely over land areas, with increased chances of above-normal temperatures dominating .... A global warming trend also contributes to the sea surface temperature and air temperature forecast," it said.
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