A cold snap has covered parts of Australia's east coast with a blanket of snow, in the middle of spring.

Motorists were left stranded in the Blue Mountains west of Sydney, while power lines were downed, trees uprooted and ferries cancelled due to high winds and hail in coastal areas.

Residents in Katoomba described the snowfall as the heaviest they had seen.

Forecasters predict the cold weather will give way to warmer temperatures over the weekend.