The federal government's agriculture forecaster has released its September crop report which has revised its winter crop prediction down by seven per cent from June.

Forecast production is around 16 per cent below the 10-year average to 2018/19, while the year-on-year figure is up 11 per cent.

There are mixed fortunes across states, with timely rainfall in WA helping to boost prospects across most of the state.

In Queensland and NSW where drought has been widespread, the Australian Bureau of Agricultural and Resource Economics and Sciences predicts winter crop production will be "very much below average".

According to the Bureau of Meteorology, rainfall in September and October is likely to be below average in most regions, with WA the exception.

In SA, rain in most major cropping regions in the state's south and mid-north got sufficient rainfall, putting them in reasonable shape.

But northern SA regions have below average prospects.

In Victoria, most crops are in good to very good condition at the beginning of spring as a result of generally favourable growing conditions over winter.

ABARES acting Executive Director Peter Gooday said the outlook for early spring in eastern Australia was likely to constrain crop prospects in southern NSW and northern cropping regions in Victoria and SA.

"Early spring rainfall will be important to final crop outcomes," he said.

He said what and canola were forecast to increase 10 and six per cent respectively over the year, but both were expected to be significantly below the 10-year average.

Barley production is forecast to increase by 14 per cent to around 9.5 million tonnes which brings it six per cent above the 10-year average.

Mr Gooday said the outlook for summer crops was unfavourable due to poor seasonal conditions in northern NSW and Queensland.

Australian Associated Press