The Bay Area Air Quality Management District issued a Spare the Air alert for smog on Tuesday.
Hot inland temperatures in the June 21 forecast are expected to combine with motor vehicle exhaust to create increased concentrations of smog.
The alert is the second so far this year.
Officials advise people to carpool or find alternatives to driving to reduce vehicle exhaust in the air.
"As our roadways grow increasingly congested, it's important we all understand the significant health, quality of life and air quality impacts that can be attributed to driving," said Sharon Landers, interim executive officer of the Air District, in a statement.
Officials also suggest completing strenuous activity in the morning, when ozone concentrations are lower because high concentrations can cause congestion, throat irritation and chest pains. It can also trigger illnesses like asthma and is harmful to those with heart and respiratory conditions.
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People receive notifications about Spare the Air alerts by registering for emails at www.sparetheair.org, downloading the Spare the Air app, finding Spare the Air on Facebook or Twitter or calling (800) HELP-AIR.
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