The Bureau of Meteorology (BOM) 2019 winter outlook, released on May 30, predicts a positive IOD will develop in June and persist through winter and spring.

This will decrease the chance of northwest cloud bands, and the associated moisture, reaching southern and central Australia, meaning typically below average winter rainfall and snowfall.

In a negative scenario more moisture in the northwest coast of Australia would travel in cloud bands tracking across the Kimberly and across Australia, Mr Graham said

However, six of the international climate models surveyed by the BOM indicate a positive during June. The last recorded positive year was in 2015.

Both the Indian Ocean and Great Southern Ocean are powerful indicators of weather systems in winter and early spring, Mr Graham said.

The BOM's forecasts expect that the Indian Ocean is the dominant influence, and those developments are more "worrying" than the developments in the Pacific Ocean.

This does not mean no rainfall over winter, but without a strong cloud band the outlook is for a drier than average winter. If these developments persist into July it will likely increase the chance of a drier than average spring, Mr Graham said.

A positive also means lower snowfall in late winter and spring.

BOM's manager of long-range forecasting Dr Andrew Watkins said, "drier than average conditions typically mean more cloud-free nights, which increases the risk of frost in susceptible areas."

Dr Watkins said temperatures across the rest of winter were very likely to be warmer than average for most of eastern Australia, and for much of the country.

"Our climate outlook shows most states and territories have large areas where chances are greater than 80 per cent for warmer than average days," he said.

"Winter nights are very likely to be warmer than average in Tasmania, along the mainland's southeast coast, and northern WA stretching through parts of the NT."

The chance of exceeding the median rainfall in the Southern Tablelands in June is unlikely, according to the BOM.

Forecasts for June shows there is a 75 per cent chance of more than 25 millilitres (mL) of rainfall for the Yass Valley and the Upper Lachlan Shire. In Queanbeyan-Palerang and Goulburn Mulwaree there is a 75 per cent chance of more than 10mL of rainfall.

The median rainfall for parts of Yass Valley is 56mL and the Upper Lachlan Shire is 58mL. In Goulburn the median is 36mL and in Braidwood is 33mL.

In April, the BOM's rainfall data from Braidwood, Goulburn, and Taralga show these areas recorded the lowest total rainfall for twenty years.

However, rainfall in May impacted positively on much of the Southern Tablelands.

The BOM's autumn summaries will be released on Monday, 3 June.