Nearly 600 firefighters were on the lines Wednesday, backed by at least a dozen aircraft and nearly three-dozen fire trucks, but the blaze was only 5 percent contained in the steep, rugged terrain.
Flames approached the canyon's two-lane highway in places during the night but crews were able to light backfires to remove fuel from its path, officials said Wednesday morning.
"This is a good start. We've got a real good chance of holding the line," said Larry Sears, the divisional commander who lead the backfire operation team.
The fire was approaching the area of Slide Rock State Park, a popular recreation spot that draws hundreds of thousands of visitors a year.
If it jumps the highway "then it's a whole new ball game for trying to catch the fire," said Sears. Officials said the fire could be drawn up the other side of the canyon and into thick wilderness.
The fire started Sunday as a campfire and spread quickly, forcing the evacuation of about 400 homes and businesses in the canyon more than 90 miles north of Phoenix. Residents of 180 homes on the north side of Sedona, who were evacuated Sunday, were going to be allowed to return Wednesday, said incident commander Paul Broyles.
Elsewhere, crews in Colorado battled an 8,960-acre wildfire that forced the evacuation of more than 300 homes. U.S. 160 through the area was closed Wednesday for a third day.
Lighter wind, lower temperatures and slightly higher humidity were forecast for the area. "It will be a cool, moist surge" moving in Wednesday night, said National Weather Service meteorologist Kathy Torgerson.
The fire, ignited by lightning and reported Sunday, was located near Fort Garland, about 150 miles south of Denver.
"I've never seen a fire that size," Myers Archoata said as he sat in his pickup along U.S. 160. "I've lived here all my life. We've had fires, but we've been able to put them out."
In Santa Maria, Calif., firefighters battled a 10,000-acre blaze that had stopped short of a critical ridgeline in Los Padres National Forest. No homes were threatened as the fire burned away from the small town of New Cuyama, about 45 miles east of Santa Maria.
Wildfires have charred more than 3.1 million acres nationwide so far this year, well ahead of the average of about 900,000 acres by this time, the National Interagency Fire Center reported. Huge grass fires that swept Texas and Oklahoma this spring account for much of the increase.