Doctors advise residents in the area, especially those with health conditions, the elderly and young children, to stay indoors in a filtered-air environment with windows closed.
Those who have to be outside should wear a surgical-type mask or at the very least a wet bandana over their nose, said Dr. Ray Casciari, a pulmonology specialist with St. Joseph Hospital in Orange.
"The message for the folks at home is this is a dangerous situation," Casciari said. "Air quality is really bad throughout all of Orange County."
The South Coast Air Quality Management District has issued a smoke advisory for most of Orange County as well as the Corona/Norco area of Riverside County.
"Smoke is currently heavy in the vicinity, with the fire fueled by strong Santa Ana winds," the AQMD said. "Winds will remain from the east today bringing smoke into portions of Orange County. Air quality may reach unhealthy levels or higher in areas directly impacted by smoke."
Casciari said the concern is about particulates getting into the lungs, especially when breathed in through the mouth.
"It's the deep breathing that takes the particulates deeper into your lungs," he said.
"This is a bad situation," he said. "It's a temporary situation. Stay indoors, use your air conditioner. Don't exercise unless you absolutely have to. And if you do (go outside), wear a mask."