EnviroNearby

La Plata County, Colorado air quality history

Daily Air Quality Index summaries from EPA monitors in La Plata, Colorado, 1990–2025.

61%
Good days in 2025
48
Median daily AQI, 2025
2
Days above 100 in 2025
365
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for La Plata, Colorado on 365 days. 222 of those days (61%) were in the Good range, and the median daily AQI was 48. That median is about the same as the typical monitored county in Colorado (median 46 across 27 counties), and higher than the typical monitored U.S. county (40). The main pollutant was ozone on 349 days. Across the years with fuller monitoring, the share of Good days fell: an average of 92% in 1990–1992 versus 64% in 2023–2025.

How the days broke down each year

Each bar is one year. The colored segments show the share of monitored days that fell in each AQI category.

Share of monitored days in each AQI category, by year0%25%50%75%100%1990: Good 323 of 344 days1990: Moderate 21 of 344 days19901991: Good 339 of 349 days1991: Moderate 10 of 349 days1992: Good 308 of 363 days1992: Moderate 55 of 363 days1993: Good 297 of 361 days1993: Moderate 63 of 361 days1993: Unhealthy for Sensitive Groups 1 of 361 days1994: Good 244 of 365 days1994: Moderate 119 of 365 days1994: Unhealthy for Sensitive Groups 2 of 365 days1995: Good 315 of 365 days1995: Moderate 50 of 365 days19951996: Good 283 of 365 days1996: Moderate 78 of 365 days1996: Unhealthy for Sensitive Groups 4 of 365 days1997: Good 286 of 364 days1997: Moderate 78 of 364 days1998: Good 253 of 365 days1998: Moderate 109 of 365 days1998: Unhealthy for Sensitive Groups 3 of 365 days1999: Good 235 of 364 days1999: Moderate 123 of 364 days1999: Unhealthy for Sensitive Groups 6 of 364 days2000: Good 283 of 366 days2000: Moderate 83 of 366 days20002001: Good 311 of 365 days2001: Moderate 54 of 365 days2002: Good 292 of 364 days2002: Moderate 72 of 364 days2003: Good 314 of 364 days2003: Moderate 50 of 364 days2004: Good 258 of 366 days2004: Moderate 107 of 366 days2004: Unhealthy for Sensitive Groups 1 of 366 days2005: Good 222 of 365 days2005: Moderate 138 of 365 days2005: Unhealthy for Sensitive Groups 5 of 365 days20052006: Good 231 of 365 days2006: Moderate 124 of 365 days2006: Unhealthy for Sensitive Groups 10 of 365 days2007: Good 211 of 365 days2007: Moderate 148 of 365 days2007: Unhealthy for Sensitive Groups 6 of 365 days2008: Good 208 of 366 days2008: Moderate 153 of 366 days2008: Unhealthy for Sensitive Groups 5 of 366 days2009: Good 255 of 365 days2009: Moderate 104 of 365 days2009: Unhealthy for Sensitive Groups 6 of 365 days2010: Good 220 of 365 days2010: Moderate 135 of 365 days2010: Unhealthy for Sensitive Groups 9 of 365 days2010: Unhealthy 1 of 365 days20102011: Good 208 of 365 days2011: Moderate 147 of 365 days2011: Unhealthy for Sensitive Groups 10 of 365 days2012: Good 218 of 366 days2012: Moderate 146 of 366 days2012: Unhealthy for Sensitive Groups 2 of 366 days2013: Good 232 of 365 days2013: Moderate 128 of 365 days2013: Unhealthy for Sensitive Groups 4 of 365 days2013: Very Unhealthy 1 of 365 days2014: Good 279 of 365 days2014: Moderate 85 of 365 days2014: Unhealthy for Sensitive Groups 1 of 365 days2015: Good 271 of 365 days2015: Moderate 92 of 365 days2015: Unhealthy for Sensitive Groups 2 of 365 days20152016: Good 238 of 366 days2016: Moderate 120 of 366 days2016: Unhealthy for Sensitive Groups 8 of 366 days2017: Good 255 of 365 days2017: Moderate 106 of 365 days2017: Unhealthy for Sensitive Groups 4 of 365 days2018: Good 236 of 365 days2018: Moderate 109 of 365 days2018: Unhealthy for Sensitive Groups 10 of 365 days2018: Unhealthy 7 of 365 days2018: Very Unhealthy 3 of 365 days2019: Good 267 of 365 days2019: Moderate 98 of 365 days2020: Good 273 of 366 days2020: Moderate 91 of 366 days2020: Unhealthy for Sensitive Groups 2 of 366 days20202021: Good 239 of 364 days2021: Moderate 121 of 364 days2021: Unhealthy for Sensitive Groups 4 of 364 days2022: Good 266 of 365 days2022: Moderate 98 of 365 days2022: Unhealthy for Sensitive Groups 1 of 365 days2023: Good 237 of 365 days2023: Moderate 123 of 365 days2023: Unhealthy for Sensitive Groups 2 of 365 days2023: Unhealthy 2 of 365 days2023: Very Unhealthy 1 of 365 days2024: Good 242 of 366 days2024: Moderate 122 of 366 days2024: Unhealthy for Sensitive Groups 1 of 366 days2024: Very Unhealthy 1 of 366 days2025: Good 222 of 365 days2025: Moderate 141 of 365 days2025: Unhealthy for Sensitive Groups 2 of 365 days2025
  • Good
  • Moderate
  • Unhealthy for Sensitive Groups
  • Unhealthy
  • Very Unhealthy
  • Hazardous

Typical and high-end AQI over time

The median is the middle day of the year. The 90th percentile is the level that only the highest 10% of days exceeded.

Median and 90th-percentile daily AQI, by year0501001990: 90th percentile AQI 471991: 90th percentile AQI 461992: 90th percentile AQI 581993: 90th percentile AQI 611994: 90th percentile AQI 771995: 90th percentile AQI 541996: 90th percentile AQI 611997: 90th percentile AQI 611998: 90th percentile AQI 711999: 90th percentile AQI 742000: 90th percentile AQI 592001: 90th percentile AQI 522002: 90th percentile AQI 552003: 90th percentile AQI 522004: 90th percentile AQI 712005: 90th percentile AQI 772006: 90th percentile AQI 842007: 90th percentile AQI 792008: 90th percentile AQI 802009: 90th percentile AQI 672010: 90th percentile AQI 802011: 90th percentile AQI 842012: 90th percentile AQI 802013: 90th percentile AQI 772014: 90th percentile AQI 642015: 90th percentile AQI 642016: 90th percentile AQI 802017: 90th percentile AQI 712018: 90th percentile AQI 802019: 90th percentile AQI 612020: 90th percentile AQI 612021: 90th percentile AQI 712022: 90th percentile AQI 712023: 90th percentile AQI 712024: 90th percentile AQI 742025: 90th percentile AQI 741990: Median AQI 321991: Median AQI 321992: Median AQI 441993: Median AQI 431994: Median AQI 461995: Median AQI 401996: Median AQI 441997: Median AQI 441998: Median AQI 441999: Median AQI 462000: Median AQI 432001: Median AQI 382002: Median AQI 402003: Median AQI 402004: Median AQI 442005: Median AQI 472006: Median AQI 462007: Median AQI 482008: Median AQI 492009: Median AQI 462010: Median AQI 482011: Median AQI 492012: Median AQI 482013: Median AQI 472014: Median AQI 442015: Median AQI 432016: Median AQI 472017: Median AQI 462018: Median AQI 452019: Median AQI 442020: Median AQI 452021: Median AQI 472022: Median AQI 462023: Median AQI 462024: Median AQI 462025: Median AQI 4819901995200020052010201520202025
  • Median daily AQI
  • 90th-percentile daily AQI

Main pollutant by day, 2025

On each monitored day, the AQI reflects whichever measured pollutant had the highest index. This counts how many days each pollutant set the AQI. A pollutant that was not measured here cannot appear.

PollutantDays as main pollutantShare of monitored days
Ozone34996%
Fine particles (PM2.5)164%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
202536522214120004874112Ozone
202436624212210104674240Ozone
202336523712322104671211Ozone
20223652669810004671108Ozone
202136423912140004771140Ozone
20203662739120004561133Ozone
2019365267980000446187Ozone
2018365236109107304580243Ozone
201736525510640004671112Ozone
201636623812080004780122Ozone
20153652719220004364108Ozone
20143652798510004464101Ozone
201336523212840104777293Ozone
201236621814620004880108Ozone
2011365208147100004984150Ozone
201036522013591004880183Ozone
200936525510460004667125Ozone
200836620815350004980112Ozone
200736521114860004879140Ozone
2006365231124100004684126Ozone
200536522213850004777140Ozone
200436625810710004471108Ozone
2003364314500000405288Ozone
2002364292720000405583Ozone
2001365311540000385271Ozone
2000366283830000435990Ozone
199936423512360004674147Ozone
199836525310930004471126Ozone
1997364286780000446187Ozone
19963652837840004461126Ozone
1995365315500000405484Ozone
199436524411920004677122Ozone
19933612976310004361101Ozone
19923633085500004458100Ozone
1991349339100000324671Ozone
1990344323210000324780Ozone

What this data can and can’t tell you

It is a county-level summary. EPA reports one AQI per day for the county, based on the monitors operating there. Air at a particular street, school or home can differ, especially near roads, industry or wildfire smoke.

It is not a health assessment. The AQI is EPA’s scale for communicating daily air quality. A county’s history can’t tell you what the health risk is for any particular person. For daily conditions and health guidance, see AirNow.

Rules change over time. EPA has revised AQI breakpoints, most recently for fine particles in 2024, so some year-to-year change can reflect the scale rather than the air.

Counties in Colorado with a similar median AQI in 2025

All monitored counties in Colorado

Source: U.S. EPA AirData, “Annual AQI by County” files for 1990–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem