The blaze, dubbed the Canyon Fire by authorities, ignited just after 1pm in Chino Hills State Park on Monday.
The Orange County Fire Authority said the fire grew to 2,500 acres overnight as 500 homes were evacuated.
More than 300 firefighters worked through the night to calm the flames and make sure residents reached safety.
Four schools have been closed, while an evacuation centre has been opened in a fifth school for those needing shelter.
The Orange County Fire Authority said at least one building has been damaged or destroyed, while multiple structures are under threat in Corona.
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Cora Angeles, who was evacuated, told the LA Times: “We don’t know what’s going to happen.
“At least we know we’re going to be alive because we got out of there in time.”
Fire official Captain Steve Concialdi said evacuation orders will be lifted “sometime today”.
He said the flames cleared much of the fuel that endangered homes, but that fire fighters will be fighting the blaze amid a 90-degree heat, gusty wind and dry air.
He added: “It’s just getting hotter and drier.”
Just five per cent of the fire was contained as of early Tuesday morning, according to officials.
Nine helicopters and nine fixed-wing aircraft along with 350 firefighters are currently battling the flames.
The blaze has resulted in a smoke advisory for northern and central Orange County, as well as the cities of Corona and Norco in Riverside County.
There have been no reports of injuries and the cause of the blaze is unknown.
The Canyon Fire comes just weeks after Los Angeles witnessed its largest wildfire to date.
The nearly 5,900-acre La Tuna Fire forced more than 1,400 people to evacuate their homes in early September.
And on Sunday, California was rocked by 28 earthquakes in just 24 hours sparking fears a major magnitude 8 quake could strike.