Australia's north-east coast was hit by heavy rains, wild winds and huge seas for the fifth straight day on Tuesday, forcing widespread evacuations.
As water levels continued to rise and heavy overnight rains shut low-lying roads, New South Wales state emergency services directed hundreds of residents in regional towns to move to safer places.
The cyclonic conditions, generated by an intense low-pressure system off the Queensland coast, swallowed beaches and submerged large areas of the heavily populated regions between the NSW and Queensland state borders.
Quiet seaside suburbs were battered by the storm, with high seas destroying some of the most famous beaches, including the main beach at popular tourist spot Byron Bay in northern NSW.
The storm also whipped up thick sea foams, a rare event, along Gold Coast beaches that lured families and children to play in the bubbles, footage on social media showed.
Australia's Bureau of Meteorology said the heavy rains were expected to weaken by late Tuesday or early Wednesday but said isolated thunderstorms could still generate heavy localised falls and trigger flash floods.
Australia is passing through a summer expected to be dominated by the La Nina phenomenon, typically associated with greater rainfall and more tropical cyclones – a sharp contrast with last summer's devastating bushfires.
"We've been warned by the weather experts that La Nina will have an impact over summer in the eastern coast of Australia so we need to expect the unexpected," NSW Premier Gladys Berejiklian told ABC television.
"I'm hoping what we've seen in the last few days won't be repeated frequently over summer, but it could. Our weather experts tell us they are expecting conditions worse than what we've seen in quite a number of years."