The Bay Area Air Quality Management District had issued the alert and advisory on Tuesday because of what it called "unprecedented levels of air pollution" caused by the several wildfires burning tens of thousands of acres in Napa, Sonoma and Solano counties.
Residents should also avoid exercising outside if they smell smoke.
Winds of over 50 miles per hour spread 22 distinct wildfires in Northern California since Sunday.
"We're going to see a really strong settling of the smoke in the Bay Area on Friday and Saturday", said National Weather Service's Bay Area office meteorologist Brian Garcia. "It's going to be really bad". More than 1,000 homes have been destroyed in the Northern part of the state.
Those who are sensitive to air quality or smoke impacts - such as pregnant woman, the elderly, young children and those with respiratory illnesses such as heart or lung disease and asthma - should take additional precautions if necessary, such as closing windows and doors, turning on the air conditioner, or avoiding vigorous outdoor or indoor exertion.
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"We are proud to team up with all of the Bay Area professional sports teams to support North Bay disaster relief efforts."
Air quality before 7 a.m. Tuesday was rated as moderate in Gilroy, Concord and Livermore. Truckee, Salinas, Santa Cruz and Atascadero, all affected by the wildfires, had readings between 151 and 158, regarded as unhealthy.
The following spots in San Francisco will provide you with filtered air. Schools across the Bay area are closed.
"The control burn was planned for today, and due to conditions the control burn was canceled", he said.