The weather bureau warned of heavy rainfall potentially leading to flash floods and landslides along the east coast region from Newcastle to Bateman's Bay in New South Wales state, with rain expected to intensify over the next two days.
"We are now facing dangers on multiple fronts -- flash flooding, riverine flooding and coastal erosion," New South Wales emergency services minister Steph Cooke said in a televised media briefing.
She urged people to reconsider holiday travel, with the rough weather having hit at the beginning of school holidays.
"This is a life threatening emergency situation," Cooke said.
More than 200 millimeters (8 inches) of rain have fallen over many areas with some hit by as much as 350 millimeters, 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 modeling showed the spill would be comparable to a major spill in March 2021 at the Warragamba Dam.
"There's no room for the water to remain in the dams. They are starting to spill. The rivers are flowing very fast and very dangerous. And then we have the risk of flash flooding, depending on where the rains are," State Emergency Service Commissioner Carlene York said.
A local takes a photo of a road inundated by floodwaters in Camden in South Western Sydney, Sunday, July 3, 2022.
In the past day, 29 people have been rescued from floodwaters, including one who was hanging on to a pole for an hour as workers struggled to reach them.
The Australian government has provided the state with 100 troops who are helping with sandbagging and two helicopters to aid with any rescues, Defense Minister Richard Marles said on Sky News.
