San Luis Obispo, California Air Quality
San Luis Obispo County, California (CA)
↓ Improvingover 10 years
How San Luis Obispo, California Air Quality Compares
San Luis Obispo, California's median AQI of 47is 15% worse than the national average of 41. Air quality has improved by 13 AQI points over the past decade. The area averages 10 unhealthy air days per year. The primary pollutant of concern is Fine Particulate Matter (PM2.5).
San Luis Obispo, California Air Quality: The Full Picture
San Luis Obispo, California (San Luis Obispo County) holds an AirHistory Air Quality Grade of C (fair, scoring 63 out of 100), built from 10 years of EPA Air Quality System monitoring. Its median AQI fell 13 points between 2014 (60) and 2023 (47), and the five-year median now sits at 51 — 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 115 of 365 monitored days (32% of the year), making it the controlling pollutant for the C grade. The single worst reading logged that year hit an AQI of 122 (Unhealthy for Sensitive Groups), while the 90th-percentile day — the level the dirtiest 10% of days reach — came in at 77.
In 2023, San Luis Obispo County recorded 207 "Good" air days (57% of the 365 days with valid AQI data), 152 "Moderate" days, and 6 days at "Unhealthy for Sensitive Groups" or above. Over the most recent five years on record, monitors logged 51 days that crossed into "Unhealthy for Sensitive Groups" or worse — about 10 per year.
The decade-long trend is improving: median AQI has been dropping by roughly 1.01 points per year. The cleanest year in the record was 2023 (median AQI 47), and the most polluted was 2014 (median AQI 60). 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). This area has seen measurable air quality improvement over the decade.
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 | 47 | 77 | 122 | 207 | 152 | 6 | Ozone |
| 2022 | 55 | 75 | 115 | 117 | 245 | 3 | PM2.5 |
| 2021 | 53 | 77 | 133 | 154 | 203 | 8 | Ozone |
| 2020 | 53 | 90 | 334 | 161 | 174 | 31 | PM2.5 |
| 2019 | 49 | 74 | 108 | 196 | 166 | 3 | Ozone |
| 2018 | 53 | 77 | 133 | 147 | 209 | 9 | Ozone |
| 2017 | 58 | 82 | 133 | 107 | 250 | 8 | PM2.5 |
| 2016 | 55 | 84 | 156 | 140 | 217 | 9 | Ozone |
| 2015 | 58 | 80 | 126 | 95 | 265 | 5 | PM2.5 |
| 2014 | 60 | 87 | 126 | 81 | 270 | 14 | PM2.5 |
What This Means for San Luis Obispo County Residents
San Luis Obispo, California has received an Air Quality Grade of C (63/100) based on a decade of monitoring data from the EPA's air quality monitoring program. The current median AQI of 47 falls in the "Good" range.
Encouragingly, air quality here has been improving, with the median AQI dropping by 13 points over the monitoring period. This trend suggests continued investment in emission controls and cleaner energy.
The primary pollutant affecting this area is Fine Particulate Matter (PM2.5). Over the past 5 years, this area has averaged 10 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 Luis Obispo, California has a current median AQI of 47, which falls in the "Good" range. The area has received an Air Quality Grade of C (63/100) based on 10 years of EPA monitoring data.
Air quality in San Luis Obispo, California is improving over the past decade. The median AQI has changed by -13 points from 2014 to 2023.
San Luis Obispo, California averages 10 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 Luis Obispo, California is Fine Particulate Matter (PM2.5). This is the dominant contributor to elevated AQI readings in the San Luis Obispo County area.
San Luis Obispo, California averages 10 unhealthy air days per year. Asthma patients should monitor daily AQI readings and limit outdoor activity when AQI exceeds 100. The primary pollutant is Fine Particulate Matter (PM2.5), which is a known asthma trigger.
With a median AQI of 47 (Good), outdoor exercise in San Luis Obispo, California is generally safe year-round. San Luis Obispo, California averages 10 days per year when athletes should move workouts indoors.