Median AQI
49
Good
New Mexico · County air quality · 2025
San Juan County, New Mexico
Median AQI 49 (Good). 58.2% of monitored days rated Good, direct from EPA Air Quality System stations.
- 49
- Median AQI
- 58.2%
- Good-air days
- 0
- Unhealthy days
- 12%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, San Juan County's air is good on balance, among the more polluted 10% of US counties, a median AQI of 49 with 58.2% of 273 monitored days in the Good band, driven mainly by Ozone.
- 49
- median AQI · Good
- 58.2%
- days rated Good
- Ozone
- main pollutant
- 12%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 104.
Data updated July 2026
- Good · 159 d · 58.2%
- Moderate · 113 d · 41.4%
- USG · 1 d · 0.4%
How did San Juan County's air break down in 2025?
Across 273 monitored days, 159 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 104 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 273 days monitored. Median AQI: 49 (Good).
Insights: San Juan County, New Mexico. EPA monitors recorded a median Air Quality Index of 49 across 273 measured days in 2025, earning a Good classification and a Moderate health grade. Of those days, 159 (58%) fell in the Good band (AQI 0–50), 113 (41%) registered Moderate readings, and 1 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 77, while the worst single-day peak hit 104 (USG). Residents averaged about 17.5 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (270 days), PM10 (2 days), NO2 (1 days). Across the 2020–2025 trend window, good days shifted by -106 and the median AQI moved +4 points, placing the multi-year trajectory at worsening. The worst single reading over the 2020–2025 window was AQI 104, usg but never Unhealthy. Nearby counties show comparable readings: Bernalillo (23.7% good, AQI 59); Catron (100.0% good, AQI 8); Chaves (94.4% good, AQI 16); Dona Ana (19.4% good, AQI 70); Eddy (46.9% good, AQI 51); Lea (61.5% good, AQI 47).
Air Quality Summary
Good Days
58.2%
159 of 273 monitored days
-16.8pp vs 75% target
Max AQI Recorded
104
USG
Health Grade
Moderate
90th-pct AQI 77
San Juan County, Good days share 58.2%
National avg
Share of monitored days at AQI 0-50 (Good band).
San Juan County, Unhealthy-or-worse share 0.0%
National avg
Share of monitored days above AQI 150 (Unhealthy or worse). Bar maxes at 10% (worst-county ceiling).
AQI Day Breakdown (2025)
Distribution of 273 monitored days across EPA AQI categories.
Good
159
58%
Moderate
113
41%
USG
1
0%
Unhealthy
0
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in San Juan County.
- Ozone · 270 days · 98.9%
- PM10 · 2 days · 0.7%
- NO₂ · 1 days · 0.4%
Health Impact Assessment
Moderate
San Juan County's air quality is rated Moderate based on 58.2% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 58.2% of monitored days in 2025, with a median AQI of 49. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 270 of 273 monitored days.
5-Year Air Quality Trend
Air quality is worsening in San Juan County. Best year: 2020 (265 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 265 | 96 | 5 | 0 | 45 | 109 |
| 2021 | 237 | 120 | 8 | 0 | 46 | 126 |
| 2022 | 238 | 116 | 9 | 1 | 45 | 220 |
| 2023 | 249 | 112 | 4 | 0 | 46 | 117 |
| 2024 | 218 | 137 | 11 | 0 | 48 | 115 |
| 2025 | 159 | 113 | 1 | 0 | 49 | 104 |
How does San Juan County compare?
How San Juan County compares
Good-day share worse than US avg
San Juan County 58.2%
Bernalillo County, New Mexico 23.7%
US average 76.5%
Median AQI worse than US avg
San Juan County 49
Bernalillo County, New Mexico 59
US average 38
Unhealthy days / yr about average
San Juan County 0
Bernalillo County, New Mexico 3
US average 0
Other Counties in New Mexico
Air quality comparison for nearby counties in New Mexico.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to San Juan County.
Allegheny County, Pennsylvania
AQI 49 · 51.6% good
Arkansas County, Arkansas
AQI 49 · 51.6% good
Ashley County, Arkansas
AQI 49 · 53.9% good
Clayton County, Georgia
AQI 49 · 53.1% good
Cleveland County, Oklahoma
AQI 49 · 53.7% good
Dewey County, Oklahoma
AQI 49 · 56.6% good
What San Juan County's air means for you
The air here stays in the breathable range year-round, with Ozone the main thing to watch.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-Ozone days, the guide explains what a median of 49 means for exposure. Health guidance
- See how San Juan County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare San Juan County with its New Mexico neighbours before drawing a conclusion about the region. All of New Mexico
Based on 273 EPA-monitored days in 2025; figures reflect only days the monitors reported. Source: EPA Air Quality System annual summaries.
More Air Quality Data
Air Quality Guides
Frequently Asked Questions
What is the air quality in San Juan County, New Mexico? ▼
San Juan County has a median Air Quality Index (AQI) of 49, rated "Good." 58.2% of monitored days (159 out of 273) had good air quality in 2025.
What is the main pollutant in San Juan County? ▼
The primary pollutant in San Juan County is Ozone (O3), which was the main AQI driver on 270 days (99% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does San Juan County have? ▼
In 2025, San Juan County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 104.
Is the air quality in San Juan County getting better or worse? ▼
Air quality in San Juan County is worsening based on 5-year trends (2020-2025). Best year: 2020 with 265 good days. Worst year: 2025 with 159 good days.
What does AQI 49 mean for health? ▼
San Juan County's median AQI of 49 falls in the "Good" category. See the <a href="/guides/understanding-aqi" class="underline">AQI category guide</a> for what each range means for health.
How does San Juan County compare to other counties in New Mexico? ▼
San Juan County has 58.2% good air days. Nearby counties in New Mexico: Bernalillo (23.7% good), Catron (100.0% good), Chaves (94.4% good), Dona Ana (19.4% good), Eddy (46.9% good), Lea (61.5% good).
What is the 90th percentile AQI in San Juan County? ▼
The 90th percentile AQI for San Juan County is 77, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 104 (USG).
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.
Every figure on PlainAir 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.