The Bureau of Meteorology is predicting an east coast low could hit early next week.
The weather system could potentially bring heavy rain, gale force winds and a risk of flash flooding on Monday July 13 and Tuesday July 14.
BOM Meteorologist Helen Kirkup said by Sunday the Bureau will have a clearer picture on the severity of the storm.
"It's still unclear exactly where and how big it will be and how it will move," she said.
"At this stage it looks like on Monday and Tuesday, the Illawarra and South Coast are likely to see the impacts from this system.
"It will be a low off the coast but at this stage whether it will become an east coast low is a bit 50/50."
Southerly winds accompanied by rainfall between 25-70mm in the Southern Highlands is expected at this stage with 10-30mm in Goulburn.
If there are any concerns of flooding, BOM will likely put out warnings on Saturday.