SAN FRANCISCO (CBS SF) — Smoke from lingering Northern California fires hung over the Bay Area on Saturday and a Spare the Air alert was issued for Sunday, though officials said it was ozone — not smoke — that prompted the warning.

Drifting smoke from wildfires in Lake County and elsewhere in Northern California was reported in at least four Bay Area counties Saturday, causing concerns for people with respiratory problems.

The Marin County Fire Department urged residents to use care if exercising outdoors, especially for those with breathing disorders.

In Solano County, Fairfield police called it a “smoky day … thanks to shifting winds from Lake County” via Twitter.

Police in Palo Alto and Redwood City also reported smoke from wildfires.

Elsewhere in on the Peninsula, drift smoke was reported in Pacifica, Half Moon Bay and Woodside, according to the San Mateo County Office of Emergency Services.

Ryan Walbrun, a meteorologist with the National Weather Service, said that while the Rocky and Jerusalem fires in Lake County were still creating smoke, the majority of the smoke drifting into the Bay Area today is from wildfire activity in Trinity County, near the Oregon border.

That smoke was carried down through the Sacramento Valley by a north wind, according to Walbrun. With no storm on the immediate horizon, however, the smoke will likely linger in the Bay Area until carried out to sea by offshore breezes.

“I wouldn’t really expect any improvement tomorrow with the fires and the wind pattern,” Walbrun said. “Hopefully if we get a little west wind by Monday afternoon that will start to filter things out.”

A Spare the Air Alert was issued for Sunday due to concerns about smog, but a representative for the Bay Area Air Quality Management District said the wildfires were not a factor in that decision.

“The primary thing we’re looking at is high levels of ozone,” district spokesman Ralph Borrmann said. “The fire is a separate factor, and it’s not actually affecting air quality,” he said.

Borrmann called it counterintuitive, saying that while many Bay Area residents can smell the smoke – the particulate mass associated with that smoke is suspended in the air column at a higher altitude.

This is the third Spare the Air Alert for smog so far this year, according to district officials.

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