The Trailhead Fire 10 miles southwest of Stanley on the western edge of the Sawtooth Wilderness was 35 percent contained at 800 acres Tuesday morning.
The fire was spotted in the afternoon of July 19 and is suspected to be human caused.
Sawtooth National Forest spokesman Ed Waldapfel said the blaze was fairly inactive the last couple days but challenging terrain was inhibiting containment efforts.
"It's just in really rough, rugged country, where it's very difficult to build line," Waldapfel said.
"We needed to give our crews a break from the beating they were taking up on the rough hillsides, where they have been working for the past several days," Incident Commander Buz Vanskike said Monday. "The fire today was just creeping and smoldering, so we took advantage of the drop in fire activity."
Rain showers and higher humidity kept the blaze fairly dormant on Monday, but lightning associated with the storms sparked two additional small fires on the Sawtooth National Forest, Waldapfel said.
Four smokejumpers parachuted onto a quarter-acre fire between Observation Peak and Hanson Lakes north of the Trailhead Fire late Monday afternoon.
"That fire is controlled and they will leave it tonight," Waldapfel said Tuesday.
The other lightning-sparked fire burned about an acre north of Alturas Lake near Cabin Creek before it was extinguished by crews from the Ketchum Ranger District and Sawtooth National Forest.
A total of 170 people were working on the Trailhead Fire Tuesday morning and two additional hand crews were expected to arrive Tuesday afternoon to help expand the line, Waldapfel said.
"These crews will be able to help us tackle some of the toughest portions of this fire," Vanskike said. "We still have some open line, but where it's located it's really tough, rugged and slow going.
"These two crews will provide a real boost once they arrive on the line."
Two water-dropping helicopters and a water truck were providing support on the fire.
Wadapfel said resources have been hard to corral since numerous wildfires are raging across the West.
"There are a lot of other fires going on, and because this fire is not threatening structures and lives, it's a little lower on the totem pole as far as getting resources," Waldapfel said. "But we just have to be patient and wait in line."
On Tuesday, 13 wildfires were burning in California, 11 in Nevada, seven in Idaho and six in Oregon.
A fire seven miles north of Arco was 10 percent contained at 375 acres on Tuesday. The 940-acre Elkhorn Fire, which last weekend was threatening homes northeast of the town of North Fork in the Salmon-Challis National Forest, was 60 percent contained Tuesday.
So far this year wildfires in the United States have consumed almost twice as many acres as average. As of July 25, a total of 68,775 fires had charred over 5 million acres. The 10-year average for this date is 49,127 fires burning 2.8 million acres.
Last September, the Valley Road Fire burned more than 40,000 acres in the White Clouds Mountains east of the Sawtooth Valley. Fueled by massive swaths of dry, beetle-killed trees, it was the largest fire in the history of the Sawtooth National Forest.
The Trailhead Fire has burned through only a few isolated, small pockets of beetle-killed trees, Waldapfel said. Full containment is expected this Friday, July 28.
Forest Service Law Enforcement and Investigation is asking anyone who was in the Trailhead Fire area from July 16 to 19 and who may have any information about the cause of the fire to contact them at (208) 373-4296.
