What Is the Air Quality in San Diego, California?

San Diego, California earns a D — air quality falls below the U.S. average, with a 5-year median AQI of 67. Residents with asthma, COPD, heart disease, or young children should watch daily AQI forecasts and limit outdoor exertion when alerts go out.

San Diego, California's 5-year median AQI of 67 is 26 points above the national average of 41 — meaningfully more polluted than the typical U.S. metro tracked here. Within California, San Diego, California runs more polluted than the state average of 49 — local sources or geography are concentrating pollution above the state's typical reading.

For context within California: Humboldt, California currently holds the state's cleanest grade (A, AQI 28), while Inyo, California sits at the bottom (F, AQI 57).

Air quality in San Diego, California has held roughly steady over the past decade, with year-to-year shifts in median AQI of less than half a point. That stability makes the city's long-run grade a reliable signal of what residents can expect day-to-day.

In 2014, San Diego, California posted a median AQI of 65. By 2023 that figure was 67 — a rise of 2 AQI points dirtier across 10 years of EPA records.

Across the past five years, this area has logged 160 days where AQI rose into the "Unhealthy for Sensitive Groups" range or worse — about 32 days per year, or roughly one every five to seven days. That is well above the national norm and explains the D grade.

Treat daily AQI forecasts as essential input. On flagged days, sensitive groups (asthma, COPD, heart disease, pregnancy, young children, older adults) should limit outdoor exertion and keep windows closed. A HEPA air cleaner sized to a bedroom or family room can cut indoor PM2.5 by 80%+ during smoke or pollution events. Because PM2.5 penetrates deep into the lungs and bloodstream, an N95 or KN95 mask provides meaningful protection on smoky or high-particulate days — surgical masks do not.