Hundreds of homes inundated in NSW

Hundreds of homes have been inundated in and around Australia's largest city in a flood emergency that was impacting 50,000 people, officials said.

Days of torrential rain have caused dams to overflow and waterways to break their banks, bringing a fourth flood emergency in 16 months to parts of the city of 5 million people.

The New South Wales state government declared a disaster across 23 local government areas overnight, activating federal government financial assistance for flood victims.

Severe weather warnings of heavy rain remained in place across Sydney's eastern suburbs. The worst flooding was along the Hawkesbury-Nepean river system along Sydney's northern and western fringes.