Fires across Australia's most populous state have been contained for the first time in nearly six months, authorities said on Friday, as heavy rains aid firefighters and boost some dam levels to their highest in nearly two years.

Australia has been battling hundreds of blazes since September in an unusually prolonged summer wildfire season that was fuelled by three years of drought, which experts have attributed to climate change.

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Aided by storms that lashed Australia's east coast earlier this week, the New South Wales (NSW) Rural Fire Service (RFS) said 24 blazes remain alight across the state, though all are now under control.

"After what's been a truly devastating fire season for both firefighters and residents who suffered through so much this season, all fires are now contained in New South Wales. Which is great news," Rob Rogers, NSW RFS deputy commissioner, told the Australian Broadcasting Corp.

Almost 150 fires

The current situation is a far cry from the peak of the crisis in early January when NSW firefighters were battling almost 150 fires that produced a fire front about 6,000 kilometres (3,700 miles) long.

Blazes across the country have razed nearly 12 million hectares (29.7 million acres) of tinder-dry bushland, killing 33 people and an estimated one billion native animals, since September.

The fires destroyed thousands of homes and prompted mass evacuations of both locals and tourists under apocalyptic-like red skies during Australia's peak summer holiday period.

As well as aiding firefighting efforts, the deluge of rains has boosted dam levels across NSW, home to more than seven million people.

With little rain for three years, some parts of the state had less than a year's worth of drinking water left, forcing some authorities to begin to truck in expensive freshwater from other parts of the country.

But nearly 400mm (15.8 inches) of rain fell in the Sydney area and surrounding areas.

The Warragamba Dam, which supplies about four-fifths of Sydney's water, is now 76.5 percent full - up more than a third in just the last week - and the highest level since April 2018.

Further rains are also expected to arrive over the coming days, with more than 50mm (two inches) of moisture across the state over the next five days.