(CBS/AP)-- They need moisture to fight wildfires in Southern California. Since Monday, firefighters have been battling a huge fire east of Los Angeles. So far, 42-sq. miles have burned. While thunderstorms might be part of the solution, they also present their own threat.
The blaze is burning through dry, dense vegetation with such force, that it's pulled in an army of 3,500 hundred firefighters.
"You know you look up the mountain where the fire's been burning and it's like a volcano and it just doesn't stop," said Dennis Burns, a fire behavior expert.
"I have seen some fire behavior that I've never experienced this early in the fire season," he said.
The steep frontlines of the fire are only accessible by air, by foot, and Saturday by a mountain tram.
The hotshots are working grueling 14-hour shifts.
"It's really labor-intensive," said Arroyo Grande hotshot Mike Hickey. "It's probably the hardest way to fight fires. It's the real old-fashioned way with pulaskis and chainsaws. You have to have the boots on the ground to get around the fire."
Tyler Freeman spent the night building containment lines. "It's a lot of loose dirt and a lot of slick rocks up there, so it's easy to slip around on stuff."
Scattered showers have brought some much-needed moisture. But the threat of thunderstorms and erratic winds has many on edge. Similar weather conditions killed 19 firefighters in Arizona last month.
"It just kind of makes me go back maybe a second or third time and make sure that I've done the best job that I possibly could," said Burns.
It would seem Burns carry quite a burden on his shoulders. "I don't sleep well at night," he said.
Due to all the aircraft needed to reach the blaze, the cost of fighting this fire is now over $12 million. But fire officials say they are finally gaining the upper hand and they estimate it will be fully contained by Friday