As much of south-eastern Australia lurches from an Indian summer straight into winter, it's time for snow bunnies to start digging out the skis and dusting off down jackets.

With the official start to the ski season still over a fortnight away, climate experts say the early odds favour more precipitation in alpine areas. But whether it falls as rain or the white stuff will be the clincher.

A key influence this winter is likely to be a possible La Nina event in the Pacific now that its counterpart, the El Nino, has ended. La Nina years are marked by above-average rain over most parts of Australia as strengthening easterly trade winds shift rainfall patterns.

"Rain - that's always the real killer for snow," Andrew Watkins, manager of climate predictions for the Bureau of Meteorology, said. "La Ninas can be a little too warm overnight and you can get rain on the snow - more so at the end of the season."

Bureau researchers including Dr Watkins found that seven of the last eight La Nina years produced below-average snow seasons, at least as measured by maximum snow depths at Spencers Creek in the NSW Snowy Mountains, which sits at 1830 metres above sea level.

Still, "things are looking more favourable than at this time last year," Dr Watkins added, noting "it only takes one or two snow dumps and you can get an OK season".

Last year got off to a slow start just as the El Nino - with its signature drop in rainfall for eastern Australia - got going. (See chart below of Spencers Creek 2015 snow depths.)

Conditions supporting a good season in 2016 for precipitation at least include developments in the Indian Ocean, with weather patterns favouring increased convection off north-western Australia. The extra moisture expected to stream over the continent has the potential to fall as snow if temperatures drop far enough.

A series of cold fronts, meanwhile, has finally broken the late-season warmth in many regions.

So far this month, Melbourne's maximum temperatures have been running at the May average for Sydney, while the Harbour City's days have been more typical of May in Brisbane.

While natural variations can swing any particular season, the longer-term trend is for a more shallow peak depth of snow and an earlier end as snow turns to rain.

The bureau's researchers have found both maximum snow depth and total snow accumulation have dropped over the past 25 years. (See chart below of snow depth.)

Of course, the resorts themselves aren't entirely reliant on fickle weather.

Advances in technology mean snow making can now happen at temperatures above zero, Dr Watkins said.

That's fine for skiers - provided it doesn't rain.