Aerial footage shows heavily flooded parts of Sydney

STORY: Thousands of residents were ordered to evacuate southwest Sydney, with torrential rain and damaging winds pounding the east coast and threatening floods in areas that were hammered in March.

More than 8 inches of rain have fallen over many areas with some hit by 14 inches, the Bureau of Meteorology said, warning of flood risks along the Nepean River.

The heavy rains caused Sydney's main dam to spill overnight, water authorities said, adding that modelling showed the spill would be comparable to a major spill in March 2021 at the Warragamba Dam.