THE Bureau of Meteorology (BOM) is forecasting a high chance of below average rainfall for large areas of Australia for June to August, along with warmer than usual temperatures.

According to the BOM's winter long–range forecast, warmer than usual daytime temperatures are likely almost everywhere, and warmer nights are also likely for many areas.

The BOM's extended prediction technical lead, Catherine Ganter, said there was a high chance of below average rainfall, particularly in southern areas of Australia.

"Southern areas have at least twice the normal chance of winter rainfall falling in the bottom 20 per cent of records," she said.

Ms Ganter said with drier conditions forecast, the risk of frost during winter, which is most common for southern and central Australia, was heightened for inland southern areas.

'Even though average minimum and maximum temperatures are expected to be warmer than usual this winter, there will still be times of cold wintry conditions," she said.

"This can increase the frost risk when there are still nights that are clear of cloud cover.'

The BOM remains at El Nino Watch, which means around double the usual chance of an El Nino event.

According to the bureau, models show it is very likely tropical Pacific Ocean temperatures will reach El Nino levels during winter, but a shift in the tropical atmosphere is also needed to declare an El Nino event.

Ms Ganter said any change to the El Nino Watch status would not change the long–range forecast which is already trending towards warm and dry for most of Australia.

According to the BOM, Australia's autumn rainfall was about 10 per cent below the 1961–1990 average, but this was not necessarily reflected in local weather observations.