The first Spare the Air day of the season has been called for Tuesday throughout the Bay Area, an air district spokeswoman said.
The Bay Area Air Quality Management District, or BAAQMD, issues Spare the Air days when air quality is unhealthy -- often coinciding with high temperatures and high pollution levels, BAAQMD spokeswoman Kristine Roselius said.
The first summer Spare the Air day in 2010 was called in August, much later than this season's first poor air quality day, which falls on the first day of summer, Roselius said.
Forecasts show Tuesday's air quality will be unhealthy and people should try to avoid driving to reduce smog levels. People with respiratory problems, young children and the elderly should take extra precaution to avoid excessive exposure to smoggy air.
Roselius suggested people carpool, take public transit, walk or bike to destinations.
Previous years saw free transit available on high pollution days, but Roselius said the district hopes that Bay Area residents saw the benefit of public transit after using free buses or trains and now use public transit or ride shares out of habit.
In the Bay Area, warmer regions inland, such as Livermore and San Jose, see more unhealthy air quality days, but other cities still need to watch their smog output, Roselius said.
"What happens in San Francisco and Marin County affects the whole area," she said, explaining how pollutants are regional and do not recognize city or county lines.
To receive Spare the Air alerts, residents can sign up at 511.org. More than 100,000 people are already registered to receive such notifications. An iPhone smartphone application is also available for free, notifying users of air quality, forecasts and pollution levels.