A massive fire in the Cleveland National Forest prompted authorities to issue a smoke advisory for Los Angeles, Orange, Riverside and San Bernardino counties on Thursday.
The Holy Fire has scorched more than 10,000 acres and has remained 5 percent contained since erupting in the Trabuco Canyon area near the border of Orange and Riverside counties on Monday afternoon, according to authorities.
The South Coast Air Quality Management District said downslope winds overnight and early morning could bring smoke into the valleys west and southwest of the flames.
The agency issued a warning, effective through Friday morning, for the following communities:
L.A. County: San Gabriel Valley
Orange County: north and central O.C., including the coast; Saddleback Valley; Capistrano Valley
Riverside County: Corona/Norco, metropolitan Riverside, Perris Valley, Lake Elsinore, Temecula Valley, Hemet/San Jacinto Valley, Banning Pass
San Bernardino County: northwest, southwest, central and east San Bernardino Valley; west, central and east San Bernardino mountains
L.A. County health officials also advised people with medical conditions and living or working in the Santa Clarita Valley to avoid outdoor activities.
"If you smell smoke or see ash due to a wildfire, limit your exposure by remaining indoors with windows and doors closed or seeking alternate shelter, and avoiding vigorous physical activity," SCAQMD's smoke advisory said. More tips can be found on the the agency's website.