The Bureau of Meteorology has moved Australia from El Nino "watch" to "alert" in anticipation of warmer and drier weather this winter.
The upgrade means the country has around 70 per cent chance of El Nino developing this year, according to the Bureau.
Bureau of Meteorology senior climatologist Catherine Ganter said the long-range winter forecast is for drier and warmer conditions across almost all of Australia.
"And the climate conditions in the Pacific Ocean are already factored into our forecasts," she said.
The Bureau said El Nino could bring reduced rainfall for eastern Australia, warmer daytime temperatures for most of southern Australia, extreme heat and bushfire danger in south-eastern Australia.
It could also bring increased frost risk, decreased alpine snow depths, a later start to the northern wet season and reduced tropical cyclone numbers.
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"While the models show it's very likely the tropical Pacific Ocean temperatures will reach El Nino levels during winter, we have seen some movement in the atmosphere towards El Nino conditions," Ms Ganter said.
"While our El Nino alert criteria have been met, these changes will need to strengthen and sustain themselves over a longer period for us to consider an El Nino event," she said.