Colorado · County air quality · 2025
San Juan County, Colorado
Limited EPA sample: 92 monitored days, below the 100-day floor for a full-year verdict. The figures below describe only those reported days.
- 12
- Sample median AQI
- 98.9%
- Good in sample
- 0
- Unhealthy in sample
- 92
- 100-day comparison floor
San Juan County has only 92 EPA-monitored days in 2025, below the 100-day annual floor
According to the U.S. EPA Air Quality System, San Juan County, Colorado reported 92 monitored days in 2025. That sample is too thin for a full-year air-quality grade or peer ranking. Use the figures only as the reported-day record, and check AirNow for current conditions.
Data source EPA Air Quality System (AQS)
- Monitored days
- San Juan County reported 92 monitored days in 2025, below the 100-day floor: sample-only, not a full-year peer rank.
- Sample median AQI
- Sample median AQI: 12
- Annual floor
- Annual floor: 100
Data updated August 2026
- Good · 91 d · 98.9%
- Moderate · 1 d · 1.1%
How did San Juan County's reported sample break down in 2025?
Across 92 monitored days, 91 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 57 (Moderate).
EPA AQS →Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in San Juan County.
- PM2.5 · 92 days · 100.0%
Sample Coverage and Health Context
San Juan County has no annual health grade because only 92 days were reported, below the 100-day floor. The 98.9% Good-day share describes only that sample.
Reported days do not reveal what happened during unmonitored parts of the year, including seasonal smoke, ozone, or inversion periods. Use these values as a description of the available EPA sample only, and check AirNow.gov for current health guidance.
The dominant pollutant is PM2.5, driving AQI on 92 of 92 monitored days.
5-Year Air Quality Trend
Air quality is stable in San Juan County. Highest Good-day share: 2023 (100.0%, 120 of 120 monitored days). The 2025 row is shown for transparency but excluded from the direction because it has fewer than 100 monitored days.
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 115 | 4 | 0 | 0 | 9 | 73 |
| 2021 | 114 | 5 | 0 | 0 | 9 | 79 |
| 2022 | 115 | 4 | 0 | 0 | 10 | 75 |
| 2023 | 120 | 0 | 0 | 0 | 9 | 50 |
| 2024 | 120 | 1 | 0 | 0 | 9 | 51 |
| 2025 | 91 | 1 | 0 | 0 | 12 | 57 |
Data Sources
Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by County dataset, 2020–2025 (aqs.epa.gov). For current conditions (not shown here — this page is historical annual data), see EPA AirNow (airnow.gov). See our methodology for how AQI, median, and coverage figures are computed.
Informational only, not professional advice. Data from EPA AQS. See our disclaimer. Spotted a figure that looks wrong? Report a correction.
Source: U.S. EPA Air Quality System (AQS) Annual AQI by county summary files for San Juan County, Colorado · 2020–2025
Download this county's annual AQI row as CSV , with the same EPA fields and denominator shown on this page.
Every figure on PlainAirData is rendered directly from EPA AQS air-quality monitoring data, no number is typed in by an editor. This page draws directly on EPA AQS air-quality monitoring data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.