In pictures: Oak Fire scorches California

California's Oak Fire has burned through more than 18,000 acres and destroyed more than 40 structures since it ignited near Yosemite National Park on Friday, July 22.

The challenging terrain and abundant dry vegetation fueling the wildfire has complicated efforts to tamp down its growth, Cal Fire spokesperson Cpt. Keith Wade told CNN on Monday.

The cause of the fire is under investigation.

Southern California fire officials have been expecting this summer to bring an especially challenging fire season due to the increased frequency of wildfires and the dry, hot conditions in much of the state. California is among the western states that have been suffering under a prolonged megadrought that has been heavily exacerbated by the climate crisis.