The Potato Fire, which was 60 percent contained by Wednesday night, was moving northeastward but was still a half mile away from the closest home, said Bob Dyson, a spokesman for the Apache-Sitgreaves National Forest.
"There is optimism that it may not get much closer than that — a half mile," Dyson said Wednesday night. "The fire has stayed within containment lines which is remarkable because the winds were blowing 30 to 50 miles per hour most of the day."
The wind-whipped fire had threatened five subdivisions, but only one is now in danger.
Some forest thinning in the past year may have prevented a major wildfire from ravaging the Flagstaff area, officials say.
More than 100 homes remained evacuated Wednesday night as wind-whipped wildfire threatened five subdivisions on the west side of Flagstaff, sending scores of people to shelters set up by the American Red Cross.
"The fire is roughly 200 acres. We have about eight crews on the fire right now. That's eight 20-person crews," Coconino National Forest spokeswoman Raquel Romero told CBS Radio affiliate KFYI. "It started just north of Interstate 40, southwest of Flagstaff."
Several air tankers dropped water and retardant on the fire in the hours before sundown, and four 20-member hotshot crews and numerous fire engines on the ground were trying to build containment lines around the fire.
"A subdivision called Railroad Springs ... on the southwest side of Flagstaff has been evacuated, and Lowell Observatory has been evacuated," Romero said.
By nightfall, fire officials were cautiously optimistic as winds lessened.
Dick Fleishman, a fire information officer with the U.S. Forest Servicem said Flagstaff, a northern Arizona city of more than 60,000 nestled in the midst of one of the largest pine forests in the world, was known to be at risk for fire. As a result, crews had drilled for an outbreak just like Wednesday's.
"We really got lucky, what with the winds we had and how dry it is," said Fleishman, noting that crews stationed nearby were able to start fighting the flames right away.
"We conducted a tremendous amount of prescribed burning and thinning in that area for just this scenario," she said. "Southwest Flagstaff is the most vulnerable because the wind usually comes out of the southwest. We conducted a lot of thinning around A1 Mountain, Woody Mountain and Mars Hill, and multiple evacuation drills have been done."
Winds gusting to 45 mph pushed a wildfire across 3,700 acres just north of Dinosaur National Monument in Colorado Wednesday, and residents of 15 houses were advised to leave.
"It's hot, it's windy, it's dry. We're in extreme fire danger," said Lynn Barclay, a spokeswoman for the federal Bureau of Land Management.
Fire officials have said a stump that was still smoldering after a lightning strike last week ignited the fire about 200 miles west of Denver.
South of Denver, another fire believed to have been sparked by a train quickly scorched 30 acres, forcing the temporary closure of C-470 and U.S. 85 before suburban firefighters were able to contain most of it, said Jamie Moore, Douglas County director of Emergency Management.
"It's so dry out here that it doesn't take more than a spark to start a wildfire," Moore said.
Dyson said nearly 500 firefighters were battling the Arizona fire, which authorities said was caused by lightning on June 6. There was no timetable yet for full containment.
An evacuation was ordered late Monday afternoon for 26 threatened homes in two subdivisions on the fire's northern flank. Some residents in the Chevelon Retreat and Chevelon Acres subdivisions about 10 miles north of Heber obeyed the order, while others chose to stay.
Dyson said 19 residents still refused to be evacuated and stayed in their homes Wednesday.
Among those who wouldn't leave was Eric Johnson, who has lived in the Chevelon Retreat development with his wife and 18-year-old son for five years.
He said he was staying to care for his animals, among them a 600-pound pig he couldn't get into a trailer. But with flames a half mile away on Wednesday afternoon, he said he wouldn't hesitate to change him mind about leaving.
"If it gets to the point where I have to leave, I will," Johnson said. "I'm not going to die out here."
Dyson said 26 other residents spent Tuesday night at a Red Cross shelter at Capps Elementary School in Heber, but it was not known when those people could return home.
The fire was within two miles of the homes when the evacuation order was issued.
Heber is located 140 miles northeast of Phoenix.