Firefighters battling the Colby fire in Glendora were bracing for increasing temperatures and winds that are expected to increase through the night and into Friday  morning.
The conditions add another level of difficulty for firefighters already negotiating red flag conditions and steep, winding hills.
The fire had destroyed more than 1,700 acres and at least two homes. At least two people had been hurt, including one firefighter who suffered a minor ankle injury.
Wind gusts atop Angeles National Forest ridges covered in flames could top out at 50 mph by 6 p.m. and last until 6 a.m. Friday, National Weather Service meteorologist Scott Sukup said.
 Temperatures on Thursday were expected to peak in the mid-80s between 2 p.m. and 4 p.m. before cooling overnight as humidity climbs into double digits, Sukup said. A wind advisory is in effect around Glendora until noon Friday, he said.
Although winds at high elevations are pushing the fire southwest, cooler air from the Pomona Valley is gusting in the opposite direction, Sukup said.
Los Angeles County Fire Inspector Scott Miller said Thursday afternoon that the fire appeared to be moving northwest, into canyons deeper within the Angeles National Forest and away from many area homes.
Steep terrain and dry brush are ongoing challenges in the firefight, Miller said. But as the afternoon wears on, he added, firefighters are also concerned about hot spots that may be sparked by strengthening winds.
Also complicating efforts are winding roads in the area. Miller said crews have had to scout roads before sending firefighters ahead, delaying their work.
At the far western edge of the smoke and flames, Ana Vasquez stared up at a ridgeline trying to spot her husband, who was spraying fire hoses and hacking at brush in an effort to protect an avocado grove her family has owned for more than 50 years.
Whenever her cellphone rang, it was her husband, Ed Vasquez, a retired Los Angeles County firefighter, with updates on his struggle on the steep hill.
He called every few minutes. All of their conversations were desperate.
“He’s up there somewhere and it’s getting hairy,” she said, her eyes fixed on flames marching ever closer to the grove and homes owned by Vasquez family members at the foot of the hill immediately east of a Azusa Canyon.
“We are in a mandatory evacuation zone,” she said. “But we’re not leaving  until my husband gives the word to scram.”
Also on the hill was Vasquez’s son, Stefen Vasquez, 27, a Los Angeles County firefighter paramedic. It was Stefan’s day off, his mother said, but he was recalled after the fire broke out in the San Gabriel Mountains on Thursday morning.
A few blocks to the west, dozens of firetrucks and their personnel were gathering along San Gabriel Canyon Road in Azusa as part of a strategy to prevent the fire from entering Azusa Canyon and threatening hundreds of homes in a community known as Mountain Cove. Among them was Vasquez’s son, who was in constant contact with his father by telephone.
Mandatory evacuation areas included north of Sierra Boulevard West of Glendora Mountain Road and East of California 39.
Three men  — identified by police as Clifford Eugene Henry, 22, of Glendora; Jonathan Carl Jarrell, 23, of Irwindale; and Steven Robert Aguirre, 21, a Los Angeles transient — have been arrested in connection with the fire and are being held at the Glendora city jail in lieu of $20,000 bail.
The men were hanging out near where the Colby trail meets Glendora Mountain Road — an area that is not a designated camping spot — when they started a campfire to try to stay warm, Glendora Police Chief Tim Staab said.
The men were tossing pieces of paper onto the fire, Staab said, when a gust of wind “just blew embers all over the place.”
“They got scared and ran,” Staab told The Times. “Two ran in one direction, one ran in the other.”
The men that took off together were eventually spotted by a resident, who flagged down Glendora Police Cpl. Nancy Miranda. Miranda was helping with evacuations along North Palm Drive when she was alerted to the men running in a wash alongside the road.
When she stopped the men, Miranda said, they said they were running because they were scared of the flames.
When Miranda asked the men if they had anything to do with the blaze about three miles away, they denied it, she said. But the men were disheveled — out of breath, covered in ash and they smelled of smoke.
“I knew immediately that something was off,” she said.
Miranda quickly searched their backpacks, finding marijuana and cigarettes. She took them to the Glendora Police Department, she said, with no sign of their missing friend.
That man, Staab said, was actually walking down Glendora Mountain Road when a U.S. Forest Service employee stopped and offered him a ride “because he was in a dangerous area.”
“They brought him to us. We said, ‘Hey, what were you doing up there?’ ” Staab said. “We learned he was one of the three.”
The chief said there was “absolutely no evidence that these three men started the fire on purpose.” One had apologized he said, and “was remorseful.”
It was unclear what the men were doing in the area, Staab said. Miranda said the area was sometimes frequented by transients and teenagers.
Staab said all three men were booked on felony suspicion of recklessly starting a fire. But the chief said the investigation was ongoing, and the men could face additional charges or enhancements because of the serious consequences of their alleged actions.
“They just didn’t show very much common sense this morning in starting this camp fire,” Staab said. “Especially when it’s breezy out? Especially when it’s the driest season on record? Please.”
The Colby fire started at 5:55 a.m. and quickly grew, but fire officials said they were well staffed and ready to fight it because of red flag alerts issued in response to the hot, dry weather and gusty winds.
When firefighters arrived, they immediately called a second alarm. The fire was inaccessible by engines and burning away from the road, said Jim Tomaselli of the U.S. Forest Service. 
About 700 fire personnel battled the blaze as well as more than a dozen aircraft.