Meteorologists said there was around a 50 per cent chance it could return by spring, which would could mean greater risk of flooding.
“A third consecutive La Niña could mean continued above-average rainfall on an already saturated east coast,” Climate Council director of research Simon Bradshaw said.
“The risk of extreme rainfall and flooding is also increasing with climate change.
“The former Federal Government failed to prepare communities for the east coast flooding disaster earlier this year, despite being warned.
“Australia is under-prepared. Only a very small fraction of disaster spending is committed to preparedness and resilience building.
“The new Labor Government must take steps now to get ahead of another potential summer of increased flood risk for these communities.”
Climate Council member and Emergency Leaders for Climate Action leader Greg Mullins said emergency services could be overwhelmed by a third La Niña event.
“With catchments saturated and dams at capacity, another La Niña means we must prepare for more devastating floods,” he said.
“(But) it’s also a double-edged sword; when the rains eventually stop, the prolific growth will inevitably fuel large grass fires across the interior, then bushfires as coastal forests dry out.
“Unprecedented climate-driven weather means unprecedented demands on our already stretched emergency services.”