The Bureau of Meteorology is predicting between 18 and 60 millimetres of rain across the Southern Highlands from Thursday through to Friday.
The conditions are being caused by the continuation of easterly winds, which will increase moisture in the low level of the atmosphere.
This will be followed by a frontal system on Thursday.
However Senior Forecaster Jordan Notora is warning the weather conditions could come with some problems.
Any storms could bring down trees and limbs already impacted by the bushfires.
Mr. Notara says the frontal system is likely to arrive on Thursday.