Wildfire smoke drifting from Oregon and Washington into the Bay Area has prompted an air quality advisory for San Mateo County through Friday, Aug. 7, and the Bay Area Air Quality Management District is urging residents to limit their time outdoors.

The district recommends staying inside with windows and doors closed when smoke is noticeable. Residents should set home air conditioning and car ventilation systems to recirculate mode to keep outside air from entering. Those who need filtered air can visit libraries, shopping malls or other buildings with air filtration systems.

Older adults, children and people with respiratory conditions such as asthma, emphysema and chronic obstructive pulmonary disease face the highest risk from smoke exposure, the district said.

The advisory, first issued Tuesday, Aug. 4, initially covered Tuesday and Wednesday. On Wednesday morning, the district extended it through Friday after conditions proved unpredictable.

The Air District said in its Aug. 5 advisory that pollution levels are not expected to exceed the national EPA 24-hour health standard for fine particulate matter, and a Spare the Air Alert is not in effect. But air quality could still become unhealthy at times because the amount and location of smoke at ground level is difficult to predict.

Hazy skies are possible. Residents may also notice the smell of smoke. The district warned in its Aug. 4 statement that conditions can change rapidly.

Where the smoke is coming from

Multiple uncontained wildfires in the Pacific Northwest are sending smoke into the Bay Area, according to SFGATE. The largest include the Grasshopper Fire in Oregon, the Little Giant Fire in Washington's Okanogan-Wenatchee National Forest and several destructive blazes near Spokane, Washington.

As of Tuesday, Aug. 4, wildfires in eastern Washington had destroyed at least 700 buildings and forced roughly 67,000 people to evacuate, KRON4 reported.

Local crews deployed north

San Mateo County firefighters are among those battling the blazes. CAL FIRE's San Mateo-Santa Cruz Unit said on X on Aug. 4 that Coastside Fire Engine 41 deployed to Washington as part of San Mateo County Strike Team 2275A to assist with fire suppression.

This advisory is separate from the Spare the Air Alert tied to the 143-acre Woodside Fire in Sonoma County, which expired Saturday, Aug. 1.

Residents can monitor real-time air quality conditions at fire.airnow.gov and find protective guidance at baaqmd.gov/wildfiresafety.