Homes have been flooded and almost 200 people have been evacuated after a creek burst its banks in southern New South Wales overnight.
The State Emergency Services has received over 700 calls for assistance as heavy rain and winds battered the south of the state.
Farmers are being told to be prepared to evacuate if necessary and allow plenty of time to do so.
The New South Wales Government has declared a natural disaster in the southwest of the state.
In the village of The Rock, near Wagga Wagga, close to 100 people have sought shelter in a hall after a river burst shortly flooding homes and a sewerage plant shortly after 1am (AEDT) on Saturday.
The ABC reports residents are being urged not to flush their toilets or wash.
Earlier, 98 properties near Tumbarumba were evacuated as a wall of the Mannus Dam threatened to collapse.
But a controlled water release overnight left the dam almost empty.
Engineers will assess the dam's safety on Saturday before residents can return home.
The State Emergency Service says people are ignoring warnings and putting their lives at risk.
The ABC reports the main flooding has been at Holbrook, Tarcutta, Tumbarumba, Lockhart, Coppabella, Walla Walla and Mannus.
In Queensland, strong winds have caused havoc on roads and in Victoria snow has blanketed parts of the state and flood warnings are in place.
The Bureau of Meteorology has issued flood warnings for all three states.