Meteorologist Michael Conway, of the Bureau of Meteorology, said the coldest air will arrive during Saturday afternoon with snow forecast at 600 metres in the west and south and 800 metres elsewhere. It is expected to continue into Sunday.

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Mr Conway said maximum temperatures will be well-below average with strong, gusty winds. He said the most significant rainfall will be in the west of the state with three-day totals of up to 60 millimetres.

Both the west and south coasts could expect huge, "long-period" swells of up to nine metres from late Saturday onwards, he said.

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"This may result in dangerous conditions and possible damage to infrastructure along the coast," he said.

"Long-period swells are highly energetic waves that have a longer than usual period of time between wave crests ... and can break powerfully as they approach shallow water, potentially coming as a surprise to fishers, boaters or people working on the water."

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