San Diego, California Air Quality
San Diego County, California (CA)
→ Stableover 10 years
How San Diego, California Air Quality Compares
San Diego, California's median AQI of 67is 63% worse than the national average of 41. Residents experience an average of 32 unhealthy air days per year, above the national threshold for concern. The primary pollutant of concern is Fine Particulate Matter (PM2.5).
San Diego, California Air Quality: The Full Picture
San Diego, California (San Diego County) holds an AirHistory Air Quality Grade of D (poor, scoring 36 out of 100), built from 10 years of EPA Air Quality System monitoring. Its median AQI rose 2 points between 2014 (65) and 2023 (67), and the five-year median now sits at 67 — inside the "Moderate" band on the EPA scale.
The pollutant driving most of the area's AQI readings is Fine Particulate Matter (PM2.5). In 2023, it set the daily AQI on 151 of 365 monitored days (41% of the year), making it the controlling pollutant for the D grade. The single worst reading logged that year hit an AQI of 150 (Unhealthy for Sensitive Groups), while the 90th-percentile day — the level the dirtiest 10% of days reach — came in at 101.
In 2023, San Diego County recorded 61 "Good" air days (17% of the 365 days with valid AQI data), 260 "Moderate" days, and 44 days at "Unhealthy for Sensitive Groups" or above. Over the most recent five years on record, monitors logged 160 days that crossed into "Unhealthy for Sensitive Groups" or worse — about 32 per year.
The decade-long trend is essentially flat, with year-to-year median AQI shifting by less than 0.10 points per year on average. The cleanest year in the record was 2022 (median AQI 63), and the most polluted was 2020 (median AQI 74). Because the data come straight from federally certified EPA monitors, these figures track the California county the monitors physically sit in rather than a city boundary.
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10-Year AQI Trend
The solid line shows the median AQI each year. The dashed line shows the 90th percentile (worst 10% of days).
Air Quality Day Breakdown
Number of days per year in each EPA AQI category. Green = Good (AQI 0-50), Yellow = Moderate (51-100), Orange = Unhealthy for Sensitive Groups (101-150), Red = Unhealthy or worse (151+).
Year-by-Year Data
| Year | Median AQI | 90th Pct | Max AQI | Good Days | Moderate | Unhealthy+ | Pollutant |
|---|---|---|---|---|---|---|---|
| 2023 | 67 | 101 | 150 | 61 | 260 | 44 | Ozone |
| 2022 | 63 | 97 | 156 | 42 | 297 | 26 | PM2.5 |
| 2021 | 67 | 90 | 133 | 52 | 297 | 16 | PM2.5 |
| 2020 | 74 | 108 | 192 | 33 | 284 | 49 | PM2.5 |
| 2019 | 66 | 93 | 169 | 38 | 302 | 25 | PM2.5 |
| 2018 | 67 | 100 | 143 | 28 | 302 | 35 | PM2.5 |
| 2017 | 68 | 112 | 174 | 41 | 262 | 62 | Ozone |
| 2016 | 68 | 105 | 164 | 30 | 294 | 42 | PM2.5 |
| 2015 | 65 | 102 | 156 | 46 | 278 | 41 | PM2.5 |
| 2014 | 65 | 101 | 170 | 48 | 278 | 39 | PM2.5 |
What This Means for San Diego County Residents
San Diego, California has received an Air Quality Grade of D (36/100) based on a decade of monitoring data from the EPA's air quality monitoring program. The current median AQI of 67 falls in the "Moderate" range.
The primary pollutant affecting this area is Fine Particulate Matter (PM2.5). Over the past 5 years, this area has averaged 32 unhealthy air quality days per year, days when sensitive groups (children, elderly, those with respiratory conditions) should limit outdoor activity. The American Lung Association's State of the Air report provides additional context on long-term health risks from air pollution exposure.
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Frequently Asked Questions
San Diego, California has a current median AQI of 67, which falls in the "Moderate" range. The area has received an Air Quality Grade of D (36/100) based on 10 years of EPA monitoring data.
Air quality in San Diego, California is stable over the past decade. The median AQI has changed by +2 points from 2014 to 2023.
San Diego, California averages 32 unhealthy air quality days per year over the past 5 years. On these days, sensitive groups including children, the elderly, and those with respiratory conditions should limit outdoor activity.
The primary pollutant affecting San Diego, California is Fine Particulate Matter (PM2.5). This is the dominant contributor to elevated AQI readings in the San Diego County area.
San Diego, California averages 32 unhealthy air days per year. With frequent unhealthy air days, asthma patients should use a HEPA air purifier indoors and check AQI before any outdoor activity. The primary pollutant is Fine Particulate Matter (PM2.5), which is a known asthma trigger.
With a median AQI of 67 (Moderate), outdoor exercise in San Diego, California is safe most days, though sensitive individuals should check daily AQI before intense workouts. San Diego, California averages 32 days per year when athletes should move workouts indoors.