As of 5:45 p.m., the fire located east of Poppet Flats Road and north of Pine Cove scorched about 650 acres and was 20 percent contained.
Riverside County firefighters said the fire was being fanned to the east by 15 to 20 mph gusts in steep, rugged terrain.
The blaze was first reported at 11:43 a.m. Officials said the temperature in the area was about 80 degrees and relative humidity was about 8 percent.
Officials said about 412 firefighters, two helicopters and seven air tankers were on scene.
CHP officers closed Highway 43 at San Gorgonio Avenue and Wesley Street. Northbound drivers hoping to go down from the mountain area were stopped at Poppet Flats Road.
Flames and smoke were reportedly visible on Interstate 10 in San Gorgonio Pass.