Fire crews are starting to really dislike holidays and fireworks.

Flames were jumping and firefighters hopping Saturday as a fresh batch of man-caused blazes broke out in Utah, scorching pines and scrub near Flaming Gorge and threatening vacation homes in Big Cottonwood Canyon.About 40 acres were charred in the Big Cottonwood fire that broke out at 2:10 p.m. Saturday behind the Jordan Pines Picnic Area, said Kathy Jo Pollock, Wasatch National Forest spokeswoman.

More than three dozen firefighters were constructing fire lines late Saturday afternoon and trying to divert the flames away from the dozen structures dotting the canyon, Pollock said.

"The fuss is because it's such a busy weekend, the canyons are crowded with people and they want to get a handle on it," she said.

The fire is in the Cardiff Flat-Mountain Haven area, popular for cross-country skiing, snowmobiling and tubing, about 8 miles up Big Cottonwood Canyon.

Crews extinguished two smaller fires in the canyon. Forest Service officials said the Jordan Pines fire would be contained sometime Sunday - if the winds didn't whip up and fan the flames into more timber and grass.

The canyon was closed to spectators and traffic, Pollock said. Containment time was predicted by early Sunday morning.

Although fireworks are banned on federal lands, and the Wasatch National Forest is closed to fires except in designated pits, Pollock said the blaze was being investigated as arson.

Man also is believed to be the culprit in a 200-acre fire in the Ashley National Forest, just below Flaming Gorge Dam near Dutch John.

The roaring blaze began about 3 a.m. Saturday and is consuming pinon, ponderosa, juniper and brush in its path, said Pollock. No structures are threatened.

About 120 firefighters were at the scene, and looking to the skies for a break in the weather.

"The forecast for the night is the possibility of dry lighting strikes, so it looks like we're going to be up all night," said Pollock.

Helicopters for the Wasatch National Forest were in the Ashley Forest along with air tankers, dropping water from the Green River and fire retardant on the flames.

"This one down at the dam, it's got natural breakers on two sides _ the river and U.S. 191 are both breaks," Pollock said. "The fire is apparently moving toward the dam."

Neither residents nor vacationers celebrating the Pioneer Day holiday were evacuated from either Big Cottonwood Canyon or Dutch John, she said.

Crews and equipment from the Forest Service, Job Corps, Salt Lake County, Salt Lake City and Brighton were in Big Cottonwood trying to beat back flames threatening structures, Pollock said. A second 1-acre fire was burning across the canyon.

"Right now at this point, the fire is on private land," she said. "As far as danger to structures, they're working a fire line around that so it doesn't run into the summer home area."

The Salt Lake City/County Fire dispatch center responded to nearly 300 calls during the Fourth of July holiday. Officials blamed fireworks for the rash of calls and grass fires.

Crews extinguished a 475-acre fire near Mona, Juab County, while a 1,700-acre blaze near Salina was controlled at 6 p.m. Saturday, said Scott Boyd, Bureau of Land Management fire dispatcher in Richfield.

"We had a lot of lightning, a little bit of rain" Saturday, Boyd said. "It just hammered us."

But any rain through Monday likely will be hit and miss, the National Weather Service said.

Parched vegetation, dry lightning and strong winds are pushing flames in dozens of fires throughout the West.

National Park Service officials evacuated two areas in Yellowstone Park because of fires and intermittently closed the south entrance.