A deluge of rain over the past week has resulted in Sydney's dams reaching their highest total since April 2018, while the Rural Fire Service has announced that all of the remaining blazes had officially been contained.

Warragamba Dam was at 73.9 per cent of its capacity on Thursday evening, and the collective average supply for all of the state's dams was just over 75 per cent.

While 24 fires still remain in NSW and the ACT, none are burning out of control after heavy rain in the southern parts of the state, where all the remaining fires are located.

"After what's been a truly devastating fire season for both firefighters and residents who have suffered through so much this season, all fires are now contained in NSW, which is great news," said Rural Fire Service Deputy Commissioner Rob Rogers.