An air quality advisory that was issued on Thursday due to wildfire smoke has been extended through Sunday, according to the Bay Area Air Quality Management District.

Smoke from wildfires in California, Oregon and Washington are expected to continue to impact the San Francisco Bay Area on Sunday. While isolated pockets of elevated pollution levels are possible, a Spare the Air alert is not in effect and pollution levels are not expected to exceed the national 24-hour standard.

California Department of Public Health (CDPH) Director and state Public Health Officer Dr. Tomás Aragón urged Californians in areas affected by wildfire smoke to take steps to protect their health, including staying indoors and reducing outdoor activity if necessary to avoid the inhalation of smoke and ash, in a news release Saturday afternoon.

"Wildfires, and the resulting smoke and ash, can be particularly unhealthy for vulnerable people, including children, older adults, those with respiratory illness or asthma, and pregnant people," said Aragón.

Officials said inhaling wildfire smoke can affect the lungs and the heart and cause persistent cough, runny nose, phlegm, wheezing and difficulty breathing. Smoke from wildfires can also cause eye irritation, reduced lung function and bronchitis. People with underlying lung or heart problems should limit their exposure by staying indoors.

People who must work outdoors for long periods, in areas with heavy smoke, or where ash is present, should wear a well-fitting N95 or P100 respirator mask, according to the CDPH.

Bay Area residents can check real-time air quality readings by visiting baaqmd.gov/highs.