The Canyon Fire has grown to more than 2,000 acres since it began Monday in the Corona and Anaheim areas near the 91 Freeway.
The South Coast Air Quality Management District said some of the strongest impacts from smoke will be felt in Corona and north and central Orange County. Unhealthy air may also be present in Los Angeles County (coastal, southern and central), Riverside County near Corona, Riverside and Lake Elsinore, and southwest San Bernardino County.
In impacted areas, people are urged to avoid vigorous outdoor or indoor exercise. People with respiratory conditions, heart disease, older adult and children are advised to remain indoors. Windows and doors should remain closed.
Other recommendations are available here from the AQMD.
AQMD spokesman Sam Atwood said during big fires, local hospitals typically see an increase in patients with asthma and emphysema.
"You see this when we have a large wildfire and we have shifting wind patterns where the winds tend to spread the smoke around a very large area," Atwood said.
The smoke advisory is expected to stay in effect at least until Wednesday morning.
"Residents should just be aware of what is the air quality in their area," Atwood said. "We're going to see smoke throughout a wide area. But in particular if you can see smoke in your area, that is a sign to not be exercising vigorously. And to stay in touch with air quality conditions."