A Spare the Air Alert has been issued for Sunday by the Bay Area Air Quality Management District because of concerns about smog.
District officials said a high-pressure system is expected to produce high temperatures, clear skies and light winds. Smog from vehicle exhaust and smoke from the Valley Fire are expected to result in smoggy skies and unhealthy air conditions.
Jack Broadbent, the air district's executive officer, advised Bay Area residents to protect their health by avoiding outdoor activities during the hottest part of the day, and any time they smell smoke.
Nearly 40 percent of smog and greenhouse gas emissions in the Bay Area come from passenger vehicles, according to air district officials, so they're asking commuters to walk, bike, carpool or take public transit.