Helicopters and air tankers flew in to battle the flames that erupted about 1:30 p.m. near the Santiago Estates Mobile Home Park in the Glen Avon area north of Pedley, said the Riverside County Fire Department.
The fire's progress was thought to have been stopped about 2½ hours later but it continued to expand. By evening it was 100 acres, with 25 percent containment, the department said.
Residents of 32 evacuated homes in the 126-unit mobile home park were allowed to return.
There were no reports of injuries or damage.
Southern California has had blustery and dry weather this week, but the winds Wednesday were southwesterly, not the sometimes fierce northeasterly Santa Anas that fan the region's worst wildfires.
Wildland fires that erupted Monday near Banning and Moreno Valley were held to a couple of acres.
