The dog days of August continue to hound firefighters battling the southern flank of the 331,375-acre Florence fire.

As temperatures rise, residents in the hamlet of Wilderness Retreat along the Chetco River more than a half-dozen miles east of Brookings have been warned to evacuate on a moment’s notice if the fire flares up along its southwest flank.

However, the fire is about three and a half miles from the scattered homes and as of Friday night remained contained by a fireline, officials said.

Firefighters on the fire’s southeast flank near O’Brien battled a 240-acre "slopover" Friday which erupted after the fire jumped a containment line.

The spot fire demonstrated the dangerous fire potential still facing the region, officials cautioned.

"We thought we got the slopover 100 percent last (Thursday) night, but it picked up again today," said Forest Service spokesman Tom Valluzzi, noting it had been fanned to life by broiling temperatures and gusting wind.

"Next week is supposed to be hot," he said, referring to weather predictions that include triple-digit temperatures in the interior valleys early next week.

"This fire ain’t over, not by a long shot," he added. "It’s going to be a long time before it’s out."

Still, the fire is now considered 20 percent contained by firelines, he added. And the evacuation notice for Illinois Valley residents has been extended to 12 hours. Favorable weather conditions have decreased the threat in the northern flank of the fire near Agness.

The fire flared up near the Quail Prairie Lookout on the west side of the Siskiyou National Forest early Friday afternoon, forcing officials to pull back firefighters in that area, said agency spokesman Bob MacGregor.

"The inversion lifted up a little — it made a little bit of a run," he said. "But it didn’t burn to our firelines. We’re pretty confident we’re going to be able to hold it."

That’s because an inversion is expected in the area this weekend, in effect putting a "blanket" on the flames, he said.

Nearly 5,500 firefighters are now battling the blaze, which covers about 463 square miles in Oregon and the far northwest tip of California.

The fire has surpassed the 1933 240,000-acre Tillamook burn but is still a far cry from the 988,000-acre Silverton fire of 1865, the largest fire in western Oregon, according to the Oregon Department of Forestry.

The fire was sparked by lightning in the Florence Creek drainage west of Selma on July 13.

Meanwhile, the fire has given crews the opportunity to deploy the PHF 20T, a converted 1960s German military tank. The vehicle is being used to snuff out hot spots that could spring up around the perimeter near O’Brien.

Built in Germany and distributed in the United States by the Texas-based Texoga company, the tank has been extensively converted for fire protection purposes. It is equipped with a 5,000-gallon water storage tank and a nozzle capable of launching 200 to 500 gallons of water every minute from a turret at its front.

A large adjustable dozer-blade also extends off the front, allowing drivers to dig or reinforce fire lines.

"We tested it for a week in Nevada and it goes great," said Jes Webb, a fire information officer. "I tried to find some place it couldn’t go and something it couldn’t go over — I couldn’t find it."

As the firefighters continue to increase containment lines around the fire, the Josephine County Sheriff’s Office will begin reuniting evacuated pets and livestock with their owners today.

The estimated 400 animals, evacuated when the fire threatened the Illinois Valley, include everything from horses to dogs and cats and at least one guinea pig, according to an office spokesman.

The Associated Press contributed to this report.

Reach reporter Paul Fattig at 776-4496 or e-mail him at pfattig@mailtribune.com