Heavy rain is pouring on parts of Australia which have been ravaged by wildfires over the last few months, offering a brief respite from the fire season.

The Bureau of Meteorology has issued flood alerts for more than 20 areas in New South Wales (NSW), with rainfall expected to last several days.

The deluge, described by Sky News' weather chief Tom Saunders as "the heaviest rain in years" has helped to douse some of the country's most damaging blazes.

“There’s going to be a huge amount of rain,” he said. “It’s enough to extinguish some of the larger bushfires but not hard enough to fill up the dams, considering how dry the catchment has been.”

More than 11.7 million hectares of land have been burned since September, in fires which have killed 33 people and an estimated 1 billion animals, and destroyed more than 2,500 homes.

Australia fires: Dust storm and flooding that followed Show all 20 1 /20 Australia fires: Dust storm and flooding that followed Australia fires: Dust storm and flooding that followed A child running towards a dust storm in Mullengudgery in New South Wales Marcia Macmillan/AFP Australia fires: Dust storm and flooding that followed Wind gusts of 66 mph were recorded as a dust storm descended over Dubbo. Storms hit many parts of Australia's western New South Wales Ian Harris via AP Australia fires: Dust storm and flooding that followed Hail covers vehicles in an intersection in Canberra. As well as dust storms, hail and flash floods have battered beleaguered Australian cities as extreme weather has diminished the threat from scores of wildfires that continue to blaze across the country's southeast Australia Institute via AP Australia fires: Dust storm and flooding that followed A dust cloud billows over a street in Dubbo Ian Harris via AP Australia fires: Dust storm and flooding that followed A man holds golf ball-size hail outside Parliament House after a severe hail storm hit Canberra EPA Australia fires: Dust storm and flooding that followed A koala holding on to a tree before it was moved to a dryer enclosure during a flash-flood at the Australian Reptile Park in Somersby Australian Reptile Park/EPA Australia fires: Dust storm and flooding that followed Bushland is seen burnt by fire as rain pools in large puddles at Bilpin, in the Blue Mountains AAP Image/Reuters Australia fires: Dust storm and flooding that followed A staff member carrying koalas during a flash flood at the Australian Reptile Park Australian Reptile Park/AFP Australia fires: Dust storm and flooding that followed A dust storm in Mullengudgery Marcia Macmillan/AFP Australia fires: Dust storm and flooding that followed A submerged car on Gold Coast AP Australia fires: Dust storm and flooding that followed Damaged cars parked outside the National Film and Sound Archive of Australia after a hail storm hit Canberra EPA Australia fires: Dust storm and flooding that followed Golf ball-sized hail at Parliament House Getty Images Australia fires: Dust storm and flooding that followed Aftermath of a hail storm at the Commonwealth Scientific and Industrial Research Organisation (CSIRO) glasshouses in Canberra EPA Australia fires: Dust storm and flooding that followed A fallen tree sits on top of a car at Caringbah in Sydney. Storms in New South Wales left more than 2,200 homes without power EPA Australia fires: Dust storm and flooding that followed Damage at the Commonwealth Scientific and Industrial Research Organisation (CSIRO) glasshouses in Canberra EPA Australia fires: Dust storm and flooding that followed Hail stones outside the Parliament House in Canberra Don Arthur/AFP Australia fires: Dust storm and flooding that followed Storm clouds gather over Sydney Harbour AFP via Getty Australia fires: Dust storm and flooding that followed Hail covers vehicles in Canberra AP Australia fires: Dust storm and flooding that followed Flooded fields on Gold Coast AP Australia fires: Dust storm and flooding that followed An aerial view as rain begins to fall on drought and fire-ravaged country near Tamworth Getty Images

However, officials have warned the wildfire threat is not yet over.

On Thursday, 42 fires continued to burn and 17 were yet to be contained, the NSW Rural Fire Service said.

"Today we were over the moon to see rain arrive across many parts of New South Wales, with decent fall in the State's north," the agency added.

It said 1,200 firefighters were working to combat the blazes.

Australia suspended its parliament on Tuesday to honour the victims of the bushfire crisis.

Scott Morrison, the prime minister, said: “This is the black summer of 2019-20 that has proven our national character and resolve.

“These fires are yet to end and danger is still before us in many, many places, but today we gather together to mourn, honour, reflect and begin to learn from the black summer that continues.”

Hundreds of protesters gathered outside of Parliament House as he spoke, criticising his government's policies on carbon emissions and the country's reliance on fossil fuels as the world's largest exporter of coal and liquid national gas.

On Monday, more than 270 Australian scientists signed an open letter demanding their government take urgent action to reduce greenhouse gas emissions.