The New South Wales Rural Fire Service called it "great news" after "a very traumatic, exhausting and anxious bush fire season so far."
The fire service's deputy commissioner Rob Rogers said it had been "a truly devastating fire season for both firefighters and residents, who've suffered through so much this season."
Firefighters said there was still some fire activity in the far south of the state, but with all fires contained, emergency workers could "really focus on helping people rebuild."
But torrential rainfall sweeping in this week -- as Tropical Cyclone Uesi tracked along the New South Wales coast -- has brought major flooding, damaging winds and dangerous surf, with severe thunderstorms forecast for the coming days.
Heavy rainfall in New South Wales has led to the evacuation of several towns and scores of schools have been closed.
The fire service tweeted Monday, however, that the rains have helped to extinguish more than 30 fires since Friday, describing it as the "most positive news we've had in some time."
The torrential rain helped put out the Currowan fire on Saturday, according to James Morris, the fire service's media officer. That particular fire burned 499,621 hectares (1.23 million acres) of land over 74 days.
Meanwhile, Sydney has seen the highest sustained run of rainfall in 30 years and some dams are at capacity, with intense rain forcing some authorities to open floodgates to relieve pressure and prevent collapse.
Australia faces a fire season every summer, but it had already had months of extreme heat and one of the worst droughts on record when this one began.
The blazes have damaged World Heritage Areas, including the Blue Mountains and the Gondwana rainforests in New South Wales and Queensland, according to Australian authorities.
The Environment Department this week released a list of 113 species considered to be at risk, including 13 birds, 19 mammals, 20 reptiles, 17 frogs, five invertebrates, 22 crayfish and 17 fish species.