Mopup operations on the Timber Crater 6 Fire at Crater Lake National Park/NPS

As the wildfire season creeps into the dog days of August, fires continue to impact national parks, with the Yosemite Valley remaining closed to all and a blaze in Grand Canyon National Park affecting a North Rim road and some trails there.

At Yosemite National Park, while the Ferguson Fire burning mostly outside the park's western borders has grown to more than 91,000 acres, fire bosses believe they've managed to sufficiently protect the Wawona area and the Mariposa Grove of Giant Sequoias from the flames.

"Completion of the firing operation south of Wawona to the South Fork of the Merced River is a significant achievement for firefighters. This successful operation will secure the community of Wawona and the Mariposa Grove," they reported Monday morning.

However, they added that, "Yosemite Valley and other nearby destinations remain closed due to increased fire activity. National Park officials reported fire has impacted all roads into the valley. Steep terrain, dense forests of beetle-killed trees, unstable slopes and other hazards have made securing the area a challenge."

Park officials said that the increased fire activity in areas adjacent to and into the park prompted the decision to extend the current park closures indefinitely. The Yosemite Valley was ordered evacuated this past Friday.

"The fire activity inside Yosemite National Park is dynamic," park staff reported Sunday evening. "Over the past 48 hours, fire has impacted all of the roads used to access Yosemite Valley, burning dead and downed trees that can become very explosive and fall without warning. There are also significant terrain hazards for firefighters. These hazards, along with extreme fire behavior and frequent weather changes, have made this an extremely difficult fire fight.

"There is active fire burning above the Arch Rock Entrance Station, moving up the Merced River Canyon towards West Yosemite Valley. There is active fire burning near Foresta and structure protection is currently in place," they added.

At the same time, a large portion of Yosemite National Park remains open. Tioga Road from Tioga Pass to White Wolf is open to all visitors and vehicles. Most of the trails and campgrounds along this route, including the Tuolumne Meadows Campground are open. Visitor services along Tioga Road, including the High Sierra Camps and the Tuolumne Meadows Store are open.

At Grand Canyon, the Cape Royal Road has been closed due to the Obi Fire, as have the Cape Final Trail, Cliff Spring Trail, the northern section of the Ken Patrick Trail from Point Imperial to Cape Royal Road, and the southern section of the Ken Patrick Trail from Cape Royal Road to the old Bright Angel Trail.

The fire on the park's North Rim covered an estimated 3,550 acres Sunday evening. The fire was moving through pine needles and downed logs. Fire behavior was active with isolated tree torching and surface fire of one to four foot flames where the fire was consuming dead logs. 

Elsewhere in the park system, Whiskeytown National Recreation Area in northern California was closed due to the Carr Fire; the slow moving Bacon Rind Fire covered not quite 500 acres, with some of that acreage inside Yellowstone National Park; while at Crater Lake National Park in Oregon the Timber Crater 6 fire covered slightly more than 3,000 acres but was 85 percent contained and crews were focusing on mopup operations.