IDYLLWILD -- The threat of weekend thunderstorms could bring much-needed moisture to a huge wildfire in the Southern California mountains near Palm Springs.
Unfortunately it could also bring wind, lightning and other volatile conditions that could make a tough firefight even worse.
Combined with hot air on the ground, the unstable air could create a strong updraft that draws smoke high into the atmosphere, fire spokesman Capt. Mike Lindbery said.
If the smoke column rises too high, moisture at the top could freeze and the weight of the ice could cause the column to collapse, creating a powerful downdraft in all directions.
"We're very concerned because this is the condition in the past that has definitely caused big firestorms and the death of citizens and firefighters," Lindbery said.
Storm cells approached the area Friday afternoon but dissipated before reaching the fire zone. But the threat would remain on Saturday and through the weekend, and fire officials hoped it would be mild cloud cover and high humidity that could help in the firefight.
The blaze in the San Jacinto Mountains had expanded to roughly 42 square miles and was 15 percent contained, U.S. Forest Service spokeswoman Kate Kramer said.
Lt. Gov. Gavin Newsom, , filling in for a vacationing Gov. Jerry Brown, declared a state of emergency for the area Friday night, freeing up more state funding and other resources to help with the protracted firefight that has already cost nearly $11 million.
Mandatory evacuations remained in place for a fourth day for about 6,000 people, and officials had advised another 700 to evacuate.
Some communities on the eastern edge of the fire were reopened to residents, but about 5,600 homes remained under potential threat.
The fire was less than two miles from Idyllwild on its western flank. It was a similar distance from Palm Springs below on the desert floor, where an enormous plume of smoke could be seen, but the blaze was showing little threat of moving toward the much larger city.
Popular campgrounds, hiking trails and a 30-mile section of the Pacific Crest Trail, which runs from the Mexican border to Canada, remained closed.
Nearly 3,500 firefighters, aided by nearly 30 aircraft, battled the fire, which stretched in elevation from 4,000 feet to 9,000 feet along the mountains, putting crews in temperatures from a comfortable 75 degrees to a scorching 110.
Authorities said the fire was human-caused, but they wouldn't say whether it was accidental or intentional. There have been no reports of injuries.
The fire, which began Monday, has burned six homes and mobile homes, one cabin, and more than a dozen other buildings.
Idyllwild resident Steve Hamlet had been watching a growing smoke cloud since Monday and evacuated his home with his 12-year-old grandson as flames crept closer.
On Friday, he worried whether he had packed the right things -- and worried about his wife, who had stayed behind.
"Do I take pictures? Do I take bills? Do I take legal documents? Or do I just take my grandson and I?" Hamlet said at a local evacuation shelter.
He and his grandson tried to check on his wife Thursday but were turned away at a road block after driving 25 miles up the mountain, he said.
"She knows enough when it's time to leave," he said.