A short hot spell in the forecast, combined with car exhaust, has prompted Bay Area air district officials to issue a Spare the Air alert for smog on Sunday.
The air pollution alert is the 18th sent out this yearby the Bay Area Air Quality Management District.
Officials hope it the alert will encourage residents to find alternatives to driving.
"Vehicle exhaust is the largest source of air pollution during periods of warm weather," said Jack Broadbent, executive officer of the air district. "Reducing driving will improve air quality and protect the climate."
A high-pressure system moving into the region is expected to bring light winds and higher temperatures on Sunday. Those conditions, along with motor vehicle exhaust, will lead to elevated concentrations of ozone, or smog, district officials said.
People can find out when a Spare the Air alert is in effect by visiting sparetheair.org, calling 800-HELP-AIR (4357-247), downloading the Spare the Air smartphone app for iPhone or Android devices or connecting with Spare the Air on Facebook, Twitter or YouTube.