Bay Area air quality officials have issued a region-wide Spare the Air alert for Saturday.
Hot temperatures and light winds are expected to result in unhealthy amounts of pollution in the air, according to the Bay Area Air Quality Management District.
Residents are encouraged to carpool, take public transit or walk to work and school rather than driving alone. Also, outdoor exercise should be limited to the cool morning hours, when smog concentrations are typically at their lowest.
"Though summer is nearly over, hot temperatures and traffic congestion continue to impact Bay Area air quality," said Jack Broadbent, the air district's executive officer.
There is no free transit offered tomorrow and there is no wood-burning ban in place.
Air quality is expected to improve by the beginning or the middle of next week as temperatures drop and winds pick up.