Smoke advisory issued: Air quality experts advise people to stay vigilant through Labor Day weekend

SAN FRANCISCO, CA - AUGUST 24: A smoky haze obstructs the view of the San Francisco skyline on August 24, 2018 in San Francisco, California. Smoke from western wildfires has settled in the San Francisco Bay Area and has pushed the air quality into unhealthy levels. (Photo by Justin Sullivan/Getty Images) less SAN FRANCISCO, CA - AUGUST 24: A smoky haze obstructs the view of the San Francisco skyline on August 24, 2018 in San Francisco, California. Smoke from western wildfires has settled in the San Francisco Bay ... more Photo: Justin Sullivan / Getty Images Photo: Justin Sullivan / Getty Images Image 1 of / 7 Caption Close Smoke advisory issued: Air quality experts advise people to stay vigilant through Labor Day weekend 1 / 7 Back to Gallery

Beware of that cool sea breeze over Labor Day weekend; it could be carrying unwanted lung-ravaging soot particles from the north.

The Bay Area Air Quality Management District issued a smoke advisory Friday warning that clouds of ash from fires in Oregon and British Columbia that are now floating over the ocean could blow ashore.

The advisory, which continues through Monday, urges Bay Area residents to limit outdoor activity, close windows and doors, and set air conditioning units and car vent systems to re-circulate if they smell smoke.

Lisa Fasano, spokeswoman for the air quality district, said smoke from the fires in our neighbor state and the province of Canada has been blowing out to sea and could waft into town this weekend.

The National Weather Service is forecasting light northerly winds through Labor Day, the same kind of breeze that blanketed the Bay Area in a brown haze during the past couple of weeks.

“We may experience smoke. It’s all very weather dependent,” Fasano said. “Because we are still experiencing smoke offshore, we could be impacted again.”

The massive fires that plagued California in July and August are mostly contained and are no longer sending smoke over the Bay Area, Fasano said.

The problem smoke is coming from Oregon, Washington and British Columbia, which is in the midst of its worst fire season on record, with 534 active fires.

Flames have blackened more than 5,000 square miles in British Columbia since Jan. 1, breaking the previous record set in 2017.

The Klondike Fire, in southwest Oregon, topped 100,000 acres this week. That blaze, which originated in the Kalmiopsis Wilderness, was 40 percent contained Friday.

“It’s really the fires up north that have the potential to impact us,” Fasano said about the smoke, which can irritate the eyes and airways, causing coughing, a dry scratchy throat and irritated sinuses.

“We’re just trying to alert the public to stay vigilant, especially children, the elderly and people with asthma and other respiratory conditions.”

Peter Fimrite is a San Francisco Chronicle staff writer. Email: pfimrite@sfchronicle.com. Twitter: @pfimrite