The 22,800-acres wildfire was about 15% contained, the U.S. Forest Service said in a statement.
Firefighters were working to protect the nearby communities as about 2,200 homes were evacuated Wednesday night.
Fire commanders leading the battle to stop the fire were concerned about a shift in the winds Wednesday night that was pushing the blaze toward the resort town of Idyllwild, said U.S. Forest Service spokeswoman Melody Lardner.
Authorities have issued evacuation notices for Idyllwild, Fern Valley and adjacent communities, the Riverside County Sheriff's Department said. The Trails End Community was under immediate evacuation notice.
Earlier, evacuation orders had been issued for areas including Apple Canyon and the Andreas Canyon Club area south of Palm Springs.
The leading edge of the blaze had been burning toward desert areas but changed direction after a frontal system began moving into the area, Lardner said.
"They are stepping up their efforts," she said of the firefighters trying to stop the flames as they burned across timber and dry chaparral.
The massive blaze has spewed large amounts of smoke and ash, prompting the South Coast Air Quality Management District on Wednesday to issue a smoke advisory for areas including Hemet, San Jacinto Valley, Banning Pass, Anza and the Coachella Valley.
Nearly 3,000 firefighters were battling the blaze as walls of flame moved quickly across mountainsides.