Median AQI
50
Good
Colorado · County air quality · 2025
La Plata County, Colorado
Median AQI 50 (Good). 53.3% of monitored days rated Good, direct from EPA Air Quality System stations.
- 50
- Median AQI
- 53.3%
- Good-air days
- 0
- Unhealthy days
- 9%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, La Plata County's air is good on balance, among the most polluted counties nationally, a median AQI of 50 with 53.3% of 304 monitored days in the Good band, driven mainly by Ozone.
- 50
- median AQI · Good
- 53.3%
- days rated Good
- Ozone
- main pollutant
- 9%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 112.
Data updated July 2026
- Good · 162 d · 53.3%
- Moderate · 140 d · 46.1%
- USG · 2 d · 0.7%
How did La Plata County's air break down in 2025?
Across 304 monitored days, 162 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 112 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 304 days monitored. Median AQI: 50 (Good).
Insights: La Plata County, Colorado. EPA monitors recorded a median Air Quality Index of 50 across 304 measured days in 2025, earning a Good classification and a Moderate health grade. Of those days, 162 (53%) fell in the Good band (AQI 0–50), 140 (46%) registered Moderate readings, and 2 (1%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 77, while the worst single-day peak hit 112 (USG). Residents averaged about 16.0 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (294 days), PM2.5 (10 days). Across the 2020–2025 trend window, good days shifted by -111 and the median AQI moved +5 points, placing the multi-year trajectory at worsening. The worst single reading over the 2020–2025 window was AQI 112, usg but never Unhealthy. Nearby counties show comparable readings: Adams (50.2% good, AQI 50); Alamosa (90.8% good, AQI 24); Arapahoe (47.3% good, AQI 51); Archuleta (79.5% good, AQI 32); Boulder (50.9% good, AQI 50); Clear Creek (64.4% good, AQI 48).
Air Quality Summary
Good Days
53.3%
162 of 304 monitored days
-21.7pp vs 75% target
Max AQI Recorded
112
USG
Health Grade
Moderate
90th-pct AQI 77
La Plata County, Good days share 53.3%
National avg
Share of monitored days at AQI 0-50 (Good band).
La Plata 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 304 monitored days across EPA AQI categories.
Good
162
53%
Moderate
140
46%
USG
2
1%
Unhealthy
0
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in La Plata County.
- Ozone · 294 days · 96.7%
- PM2.5 · 10 days · 3.3%
Health Impact Assessment
Moderate
La Plata County's air quality is rated Moderate based on 53.3% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 53.3% of monitored days in 2025, with a median AQI of 50. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 294 of 304 monitored days.
5-Year Air Quality Trend
Air quality is worsening in La Plata County. Best year: 2020 (273 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 273 | 91 | 2 | 0 | 45 | 133 |
| 2021 | 239 | 121 | 4 | 0 | 47 | 140 |
| 2022 | 266 | 98 | 1 | 0 | 46 | 108 |
| 2023 | 237 | 123 | 2 | 2 | 46 | 211 |
| 2024 | 241 | 123 | 1 | 0 | 46 | 240 |
| 2025 | 162 | 140 | 2 | 0 | 50 | 112 |
How does La Plata County compare?
How La Plata County compares
Good-day share worse than US avg
La Plata County 53.3%
Adams County, Colorado 50.2%
US average 76.5%
Median AQI worse than US avg
La Plata County 50
Adams County, Colorado 50
US average 38
Unhealthy days / yr about average
La Plata County 0
Adams County, Colorado 0
US average 0
Other Counties in Colorado
Air quality comparison for nearby counties in Colorado.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to La Plata County.
Adams County, Colorado
AQI 50 · 50.2% good
Albany County, Wyoming
AQI 50 · 51.9% good
Boulder County, Colorado
AQI 50 · 50.9% good
Davidson County, North Carolina
AQI 50 · 50.2% good
Davidson County, Tennessee
AQI 50 · 51.8% good
Gila County, Arizona
AQI 50 · 52.0% good
What La Plata 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 50 means for exposure. Health guidance
- See how La Plata County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare La Plata County with its Colorado neighbours before drawing a conclusion about the region. All of Colorado
Based on 304 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 La Plata County, Colorado? ▼
La Plata County has a median Air Quality Index (AQI) of 50, rated "Good." 53.3% of monitored days (162 out of 304) had good air quality in 2025.
What is the main pollutant in La Plata County? ▼
The primary pollutant in La Plata County is Ozone (O3), which was the main AQI driver on 294 days (97% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does La Plata County have? ▼
In 2025, La Plata County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 112.
Is the air quality in La Plata County getting better or worse? ▼
Air quality in La Plata County is worsening based on 5-year trends (2020-2025). Best year: 2020 with 273 good days. Worst year: 2025 with 162 good days.
What does AQI 50 mean for health? ▼
La Plata County's median AQI of 50 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 La Plata County compare to other counties in Colorado? ▼
La Plata County has 53.3% good air days. Nearby counties in Colorado: Adams (50.2% good), Alamosa (90.8% good), Arapahoe (47.3% good), Archuleta (79.5% good), Boulder (50.9% good), Clear Creek (64.4% good).
What is the 90th percentile AQI in La Plata County? ▼
The 90th percentile AQI for La Plata County is 77, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 112 (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.