Thick smoke from the Canyon Fire clouded the sky in Castaic, California, on Friday. The fire has burned more than 5,000 acres since its start on Thursday.

The National Weather Service said the alert will be in effect until Sunday morning in the Santa Clarita Valley and Saturday night in parts of Los Angeles, Ventura, San Bernardino, and Riverside counties.

Air quality has taken a serious hit across the United States as a two-fold blow of wildfires in the West and in Canada have sent smoke pouring across large sections of the country — a problem that’s set to linger for days.