Sydney is preparing for a deluge, with up to a month of rain expected on Saturday and Sunday.
The Hunter and Illawarra regions are also expected to experience heavy rain, with 50mm expected to fall in some parts over the next 24 hours.
WATCH VIDEO ABOVE: Heavy rain and flash flooding warned for east coast.
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The wet the weather is due to a moist air mass moving across NSW.
There is also the potential for severe thunderstorms and flash flooding in central and southern Queensland, as well as northern Victoria.
The Bureau of Meteorology is forecasting 10mm to 35mm of rain for Sydney in the remaining hours of Saturday, with a chance of thunderstorms.
Strong winds with a speed of up to 20 km/h or 30 km/h are also expected.
Sunday has a medium chance of forecast shows, most likely in the afternoon and early evening, with a chance for a thunderstorm.
In the other part of the country, forest fires continue to threaten parts of Western Australia coastline.
Locals are being advised to monitor conditions, while others are being warned not to return.
Conditions eased in Dandaragan Shire, about 200 kilometers north of Perth, after a fire sparked by a fatal car crash burned more than 70,000 hectares.
But residents who evacuated from the fishing villages of Gray Island and Wedge Island were warned not to return because of a possible threat to lives and homes.
Others are advised to continue to monitor conditions.
The Cervantes fire in the southern part of the county has been downgraded to a watch and action level.
Fire and Emergency Services Chief Damien Pumphrey urged residents to continue to monitor conditions and emergency alerts at a community briefing Friday night.
“The weather (on Saturday) and the following days is really unpredictable, bad weather and this situation could change and the warning level could go up again,” he said.
More than 200 firefighters are battling the blaze, aided by large air tankers that joined the fight on Thursday.
Portions of Indian Ocean Drive and numerous surrounding roads in the area remain closed.
The evacuation center at the Jurien Bay Sports and Recreation Center has reopened, while Nambung National Park remains closed.
