Australian authorities said on Sunday that heavy rains over the country's east coast has brought the worst flooding in half a century.
In the most populous state of New South Wales, footage showed homes uprooted by fast-moving water, trees snapped and roads were engulfed.
Emergency services estimated hundreds of homes have been damaged so far.
Several major roads were closed across the state, and some schools cancelled classes for Monday.
Dams, including Sydney's main water supply, have also spilled over, causing river levels to surge.
Gladys Berejiklian, the Premier of New South Wales, said the floods were worse than expected.
"Yesterday we were hoping it would only be a one in twenty year event, it looks like it will be a one in fifty year event."
She added that thousands of Australians have been forced to evacuate in about 13 areas of the state and 4,000 more may be asked to flee soon.
Meteorologists said the downpour is set to continue the rest of Sunday, with some areas expecting nearly 8 inches of rain.
The devastation is in stark contrast to bushfires that scorched Australia over the last two years when about 7 percent of New South Wales was scorched.