Regional air quality officials on Friday called this year's 26th smog alert for Saturday, breaking a record for the number of alerts called in a year, according to the Bay Area Air Quality Management District.
Air quality is expected to be bad because of a combination of hot temperatures, light winds and high levels of vehicle exhaust from traffic, district officials said.
"This is a wake-up call that we must reduce the number of cars on Bay Area roads," air district executive officer Jack Broadbent said in a statement. "Increased employment rates and traffic congestion underscore the need to find alternatives to driving alone."
On Spare the Air days, people are encouraged to carpool, bike, walk or take public transportation instead of driving alone. There is no free transit available Saturday and no wood-burning ban was called, according to the district.
The record for smog alerts was set in 1996, and since then the Bay Area has added a lot of jobs, a lot of new residents and a lot of single-occupancy cars on the roads, district spokesman Ralph Borrmann said.
Additionally, the U.S. Environmental Protection Agency regularly lowers the threshold for the amount of ozone, or smog, in the air that triggers a Spare the Air alert, so that as time goes on, more alerts will be called, Borrmann said.