A thick blanket of white smoke shrouded Australia's largest city on Sunday as thousands of firefighters battled to contain more than 100 wildfires.

Bush fires have raged around Sydney and other parts of New South Wales state for more than a week. On Saturday night, high temperatures and dry winds that have fanned the blazes eased temporarily and stars could be seen twinkling in the sky for the first time in days.

The moon lost its red-orange glow as a breeze pushed the fires, burning just 12 miles from Sydney, back on themselves. About 15,000 firefighters used the respite to make firebreaks and carry out controlled burns in forests and around threatened homes.

But the respite was short-lived as harsh weather returned Sunday morning when an acrid haze descended on the city's picturesque harbor and blocked out views of its famous opera house and bridge.

Officials said that temperatures could climb beyond 100 degrees Fahrenheit later Sunday, heightening the fire threat.

New South Wales Premier Bob Carr told Australian Broadcasting Corp. radio that Sunday could be "one of the most potentially dangerous days we've ever faced as a community."

New South Wales fire chief Phil Koperberg urged communities along the 370-mile fire front to remain calm. "The weather for the next 36 hours is not conducive to effective containment," he said.

According to authorities, about half of the fires burning across New South Wales were set deliberately. Five people have been arrested.

The most dangerous fires are burning in the Blue Mountains national park 50 miles west of Sydney, and along the city's southwest boundary.

More than 150 homes have been destroyed, more than 4,400 people evacuated and thousands of acres of forest and private land scorched. No deaths have been reported. Insurance officials estimate damages at more than $25 million.

National Parks and Wildlife Service director-General Brian Gilligan estimated that thousands of animals have died or have been injured, but he said it is too dangerous to try to rescue them.

"People should stay out of the parks and let nature take its course," he said.

Nearly 80 percent of the 40,000-acre Royal National Park in Sydney's south has been blackened. It is the world's second-oldest national park after Yellowstone.

Australia's forests are dominated by eucalyptus and other oil-based trees that burn easily but regenerate quickly after fires.