San Juan, Colorado Air Quality
San Juan County, Colorado (CO)
→ Stableover 10 years
How San Juan, Colorado Air Quality Compares
San Juan, Colorado's median AQI of 9is 78% better than the national average of 41. The area rarely experiences unhealthy air quality days. The primary pollutant of concern is Fine Particulate Matter (PM2.5).
San Juan, Colorado Air Quality: The Full Picture
San Juan, Colorado (San Juan County) holds an AirHistory Air Quality Grade of B (good, scoring 78 out of 100), built from 10 years of EPA Air Quality System monitoring. Its median AQI fell 1 points between 2014 (10) and 2023 (9), and the five-year median now sits at 9 — inside the "Good" 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 120 of 120 monitored days (100% of the year), making it the controlling pollutant for the B grade. The single worst reading logged that year hit an AQI of 50 (Good), while the 90th-percentile day — the level the dirtiest 10% of days reach — came in at 20.
In 2023, San Juan County recorded 120 "Good" air days (100% of the 120 days with valid AQI data), 0 "Moderate" days, and 0 days at "Unhealthy for Sensitive Groups" or above. Over the most recent five years on record, monitors logged no days that crossed into "Unhealthy for Sensitive Groups" or worse.
The decade-long trend is essentially flat, with year-to-year median AQI shifting by less than 0.05 points per year on average. The cleanest year in the record was 2015 (median AQI 8), and the most polluted was 2014 (median AQI 10). Because the data come straight from federally certified EPA monitors, these figures track the Colorado 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 | 9 | 20 | 50 | 120 | 0 | 0 | PM2.5 |
| 2022 | 10 | 26 | 75 | 115 | 4 | 0 | PM2.5 |
| 2021 | 9 | 33 | 79 | 114 | 5 | 0 | PM2.5 |
| 2020 | 9 | 31 | 73 | 115 | 4 | 0 | PM2.5 |
| 2019 | 9 | 19 | 32 | 116 | 0 | 0 | PM2.5 |
| 2018 | 10 | 33 | 100 | 109 | 9 | 0 | PM2.5 |
| 2017 | 9 | 21 | 49 | 119 | 0 | 0 | PM2.5 |
| 2016 | 8 | 18 | 31 | 121 | 0 | 0 | PM2.5 |
| 2015 | 8 | 20 | 55 | 120 | 1 | 0 | PM2.5 |
| 2014 | 10 | 22 | 37 | 118 | 0 | 0 | PM2.5 |
What This Means for San Juan County Residents
San Juan, Colorado has received an Air Quality Grade of B (78/100) based on a decade of monitoring data from the EPA's air quality monitoring program. The current median AQI of 9 falls in the "Good" range.
The primary pollutant affecting this area is Fine Particulate Matter (PM2.5). Over the past 5 years, this area has averaged 0 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 Juan, Colorado has a current median AQI of 9, which falls in the "Good" range. The area has received an Air Quality Grade of B (78/100) based on 10 years of EPA monitoring data.
Air quality in San Juan, Colorado is stable over the past decade. The median AQI has changed by -1 points from 2014 to 2023.
San Juan, Colorado averages 0 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 Juan, Colorado is Fine Particulate Matter (PM2.5). This is the dominant contributor to elevated AQI readings in the San Juan County area.
San Juan, Colorado averages 0 unhealthy air days per year. This is relatively low, making it a reasonable choice for asthma sufferers. The primary pollutant is Fine Particulate Matter (PM2.5), which is a known asthma trigger.
With a median AQI of 9 (Good), outdoor exercise in San Juan, Colorado is generally safe year-round. San Juan, Colorado averages 0 days per year when athletes should move workouts indoors.