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," Sharon Landers, interim executive officer of the Air District, said in a statement.
High temperatures are returning to Bay Area and are expected to peak over the next two days, prompting the National Weather Service to issue a heat advisory for much of the day in many inland areas.
The high temperatures are expected to last until Thursday, with the hottest conditions running from Tuesday into Wednesday, according to the National Weather Service.
There will be a moderate to high risk level for heat, primarily in the inland areas, and the heat advisory is expected to run from 10 a.m. to 10 p.m. Tuesday, according to the weather service. The highs will be in the 90s, with temperatures reaching as high as 105 degrees in the hottest areas. People are advised to stay hydrated and seek shelter from the heat, if possible.
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.
People receive notifications about Spare the Air alerts by registering for emails at sparetheair.org, downloading the Spare the Air smartphone app for iPhone or Android, finding Spare the Air on Facebook, Twitter or calling 800-HELP-AIR (4357-247).