Heavy rainfall has been forecast to ease across Australia’s east coast but floodwaters are expected to linger for days across New South Wales where 15,000 people were nervously waiting for potential orders to evacuate.

Some 18,000 residents of Australia’s most populous state have fled their homes since last week, with warnings the clean-up could stretch into April.

New South Wales premier Gladys Berejiklian said several weather fronts continued to effect large swathes of the state.

Some parts of the state have recorded two thirds of their annual rainfall in less than a week.

Prime Minister Scott Morrison said the rain emergency was expected to ease by late Wednesday, but the “floodwaters remain persistent for some time”.

“I’m advised that the rain and flood situation does remain dynamic and extremely complex,” Mr Morrison said.

Skies were forecast to clear over parts of Sydney and the coast to the north by late Tuesday.

“It is almost impossible to believe but we will see blue skies and sunshine just later this afternoon in western Sydney and on the Mid North Coast,” government meteorologist Agata Imielska said.

“It is very important to remember that even though we’ll have blue sky and sunshine returning, flooding will continue and the flood risk will continue,” Ms Imielska added.

Mr Morrison said the New South Wales government had already requested 1,000 defence personnel to help clean up after the floods.

The flooding rain had extended along the New South Wales coast across the Queensland state border in the north and almost as far as the Victoria border to the south.