The Holy Fire has spread to 6,200 acres, having jumped by about 50 percent in acreage on Wednesday.
The fire was just five percent contained, despite the effort from firefighters to contain the blaze with daylong drops by more than a dozen firefighting aircraft.
As the blaze headed toward the Lake Elsinore area, communities to the northwest of the lake in Riverside County were urged to flee their homes.
Lake Elsinore is in the western Riverside County — a natural freshwater lake about 3,000 acres in size — it is located next to Cleveland National Forest.
The McVicker Canyon, Rice Canyon, Horsethief Canyon, El Cariso, Rancho Capistrano, Blue Jay, Indian Canyon, Glen Eden, Sycamore Creek and Mayhew Canyon communities are under mandatory evacuation orders.
As is the Ortega Highway corridor from the Grand Avenue in Riverside County to Nicholas Institute in Orange County.
Cabins throughout Holy Jim and Trabuco canyons, as well as the Blue Jay and El Cariso campgrounds were under mandatory evacuation orders.
Highway 74 eastbound is closed and residents have been told the Highway 74 corridor is for westbound travel only.
Vickie Wright, a spokeswoman for the incident command team said the flames were around half a mile from those communities on Wednesday evening.
She said: “We still have a fairly good distance before homes are damaged.”
However this gap could close quickly if winds pick up, as officials warned the blaze could branch out in different unpredictable directions.
Fire crews were planning to take advantage of the weather on Wednesday night, but some areas of the blaze are difficult to access.
The blaze could affect about 7,000 residential structures, according to authorities.
No major injures have been reported but 12 structures have been destroyed.
The Holy Fire is not the biggest inferno in the state of California, but it is one of the most complex as crews have to deal with steep and rugged terrain between Orange and Riverside counties.
Fire officials were keeping an eye on the fire as it approached Santiago Peak, where communication towers are located.
A US Forest Service spokesman Steve Rasmussen said: “It’s critical infrastructure for us. It’s a major point to protect.”
The blaze has been burning since Monday. The cause of the blaze was unknown, although an arson suspect has been arrested in connection with the blaze.
California’s largest recorded — the Mendocino Complex — has spread to an area nearly the size of Los Angeles.
The deadly has destroyed more than 1,000 homes in the Redding area of Northern California and is less than 50 percent contained.