Tens of thousands of residents have been forced to flee the blaze which has destroyed hundreds of buildings as it ripped through Shasta County, some 160 miles north of Sacramento.
Around 3,400 firefighters are on the ground battling the inferno, covering 48,300 acres (19,500 hectares), while helicopters and planes attempt to tackle the flames from the air.
The fire, which is just 3% contained after starting six days ago, has been fuelled by high temperatures and low humidity, with the conditions expected to continue for at least the next week, according to fire chiefs.
Ken Pimlott, director of the California department of forestry and fire protection (CalFire), said: "This fire is a long way from done."
In addition to the two deaths, a further eight people have been injured, including three firefighters.