EnviroNearby

Park County, Colorado air quality history

Daily Air Quality Index summaries from EPA monitors in Park, Colorado, 2007–2025.

63%
Good days in 2025
48
Median daily AQI, 2025
2
Days above 100 in 2025
203
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Park, Colorado on 203 days. 128 of those days (63%) 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 203 days. Across the years with fuller monitoring, the share of Good days rose: an average of 37% in 2007–2009 versus 56% in 2023–2025.

EPA did not report an AQI for every day of 2025 here (203 of 365 days). Figures describe monitored days only; seasonal monitoring (for example, ozone measured only in warmer months) can make a county look cleaner or dirtier than a full-year record would.

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%2007: Good 61 of 199 days2007: Moderate 103 of 199 days2007: Unhealthy for Sensitive Groups 31 of 199 days2007: Unhealthy 4 of 199 days20072008: Good 32 of 123 days2008: Moderate 54 of 123 days2008: Unhealthy for Sensitive Groups 35 of 123 days2008: Unhealthy 2 of 123 days2009: Good 73 of 137 days2009: Moderate 63 of 137 days2009: Unhealthy for Sensitive Groups 1 of 137 days20092010: Good 93 of 191 days2010: Moderate 93 of 191 days2010: Unhealthy for Sensitive Groups 5 of 191 days2011: Good 219 of 307 days2011: Moderate 82 of 307 days2011: Unhealthy for Sensitive Groups 6 of 307 days20112012: Good 228 of 336 days2012: Moderate 99 of 336 days2012: Unhealthy for Sensitive Groups 9 of 336 days2013: Good 206 of 304 days2013: Moderate 97 of 304 days2013: Unhealthy for Sensitive Groups 1 of 304 days20132014: Good 232 of 338 days2014: Moderate 104 of 338 days2014: Unhealthy for Sensitive Groups 2 of 338 days2015: Good 264 of 350 days2015: Moderate 82 of 350 days2015: Unhealthy for Sensitive Groups 4 of 350 days20152016: Good 270 of 366 days2016: Moderate 93 of 366 days2016: Unhealthy for Sensitive Groups 3 of 366 days2017: Good 237 of 365 days2017: Moderate 124 of 365 days2017: Unhealthy for Sensitive Groups 4 of 365 days20172018: Good 161 of 324 days2018: Moderate 145 of 324 days2018: Unhealthy for Sensitive Groups 17 of 324 days2018: Unhealthy 1 of 324 days2019: Good 160 of 312 days2019: Moderate 150 of 312 days2019: Unhealthy for Sensitive Groups 2 of 312 days20192020: Good 187 of 343 days2020: Moderate 146 of 343 days2020: Unhealthy for Sensitive Groups 8 of 343 days2020: Unhealthy 2 of 343 days2021: Good 203 of 322 days2021: Moderate 103 of 322 days2021: Unhealthy for Sensitive Groups 16 of 322 days20212022: Good 172 of 261 days2022: Moderate 87 of 261 days2022: Unhealthy for Sensitive Groups 1 of 261 days2022: Unhealthy 1 of 261 days2023: Good 137 of 269 days2023: Moderate 129 of 269 days2023: Unhealthy for Sensitive Groups 3 of 269 days20232024: Good 172 of 323 days2024: Moderate 139 of 323 days2024: Unhealthy for Sensitive Groups 12 of 323 days2025: Good 128 of 203 days2025: Moderate 73 of 203 days2025: Unhealthy for Sensitive Groups 2 of 203 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 year0501001502007: 90th percentile AQI 1152008: 90th percentile AQI 1292009: 90th percentile AQI 772010: 90th percentile AQI 842011: 90th percentile AQI 712012: 90th percentile AQI 772013: 90th percentile AQI 712014: 90th percentile AQI 742015: 90th percentile AQI 672016: 90th percentile AQI 642017: 90th percentile AQI 672018: 90th percentile AQI 902019: 90th percentile AQI 802020: 90th percentile AQI 742021: 90th percentile AQI 842022: 90th percentile AQI 742023: 90th percentile AQI 802024: 90th percentile AQI 842025: 90th percentile AQI 772007: Median AQI 672008: Median AQI 772009: Median AQI 502010: Median AQI 512011: Median AQI 472012: Median AQI 472013: Median AQI 472014: Median AQI 472015: Median AQI 452016: Median AQI 472017: Median AQI 482018: Median AQI 512019: Median AQI 502020: Median AQI 502021: Median AQI 482022: Median AQI 482023: Median AQI 502024: Median AQI 502025: Median AQI 482007200920112013201520172019202120232025
  • 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
Ozone203100%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
20252031287320004877105Ozone
2024323172139120005084147Ozone
202326913712930005080147Ozone
20222611728711004874190Ozone
2021322203103160004884140Ozone
202034318714682005074161Ozone
201931216015020005080101Ozone
2018324161145171005190174Ozone
201736523712440004867112Ozone
20163662709330004764133Ozone
20153502648240004567112Ozone
201433823210420004774115Ozone
20133042069710004771101Ozone
20123362289990004777122Ozone
20113072198260004771126Ozone
2010191939350005184133Ozone
2009137736310005077112Ozone
200812332543520077129161Ozone
2007199611033140067115166Ozone

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 2007–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem