The Bureau of Meteorology said its climate models and indicators have now met the criteria to raise the level to "alert" from "watch" for the possibility an El Nino event.

"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," climatologist Catherine Ganter said in a statement.

"These changes will need to strengthen and sustain themselves over a longer period for us to consider an El Nino event."

The weather warnings come after Australia's chief commodity forecaster on Tuesday said the winter crop production was set to fall from record highs due to expectations of dry weather ahead.

In an El Nino pattern, there is a higher chance of drier weather in Australia's east and it would likely be warmer than usual for the southern two-thirds of Australia.

That could hit wheat production in Australia, the world's second-largest exporter of the grain, following three years of record or near-record output due to a rare, extended La Nina weather pattern, which typically brings more rain.