EnviroNearby

Montezuma County, Colorado air quality history

Daily Air Quality Index summaries from EPA monitors in Montezuma, Colorado, 1988–2025.

75%
Good days in 2025
45
Median daily AQI, 2025
1
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 Montezuma, Colorado on 365 days. 274 of those days (75%) were in the Good range, and the median daily AQI was 45. 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 363 days. Across the years with fuller monitoring, the share of Good days fell: an average of 89% in 1993–1995 versus 75% in 2023–2025.

Years with fewer than 120 monitored days (1988, 1989, 1990, 1991, 1992) are shown in the table but left out of comparisons and trend statements.

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%1988: Good 76 of 76 days19881989: Good 96 of 97 days1989: Moderate 1 of 97 days1990: Good 94 of 97 days1990: Moderate 3 of 97 days1991: Good 94 of 95 days1991: Moderate 1 of 95 days1992: Good 99 of 99 days1993: Good 220 of 229 days1993: Moderate 9 of 229 days19931994: Good 284 of 321 days1994: Moderate 37 of 321 days1995: Good 292 of 358 days1995: Moderate 66 of 358 days1996: Good 295 of 362 days1996: Moderate 63 of 362 days1996: Unhealthy for Sensitive Groups 4 of 362 days1997: Good 247 of 275 days1997: Moderate 28 of 275 days1998: Good 229 of 320 days1998: Moderate 91 of 320 days19981999: Good 228 of 346 days1999: Moderate 114 of 346 days1999: Unhealthy for Sensitive Groups 4 of 346 days2000: Good 214 of 348 days2000: Moderate 125 of 348 days2000: Unhealthy for Sensitive Groups 9 of 348 days2001: Good 257 of 344 days2001: Moderate 86 of 344 days2001: Unhealthy for Sensitive Groups 1 of 344 days2002: Good 236 of 356 days2002: Moderate 119 of 356 days2002: Unhealthy for Sensitive Groups 1 of 356 days2003: Good 245 of 357 days2003: Moderate 111 of 357 days2003: Unhealthy for Sensitive Groups 1 of 357 days20032004: Good 275 of 364 days2004: Moderate 87 of 364 days2004: Unhealthy for Sensitive Groups 2 of 364 days2005: Good 212 of 364 days2005: Moderate 142 of 364 days2005: Unhealthy for Sensitive Groups 10 of 364 days2006: Good 218 of 363 days2006: Moderate 138 of 363 days2006: Unhealthy for Sensitive Groups 7 of 363 days2007: Good 222 of 359 days2007: Moderate 134 of 359 days2007: Unhealthy for Sensitive Groups 3 of 359 days2008: Good 236 of 363 days2008: Moderate 126 of 363 days2008: Unhealthy for Sensitive Groups 1 of 363 days20082009: Good 220 of 365 days2009: Moderate 143 of 365 days2009: Unhealthy for Sensitive Groups 2 of 365 days2010: Good 265 of 365 days2010: Moderate 99 of 365 days2010: Unhealthy for Sensitive Groups 1 of 365 days2011: Good 227 of 365 days2011: Moderate 133 of 365 days2011: Unhealthy for Sensitive Groups 5 of 365 days2012: Good 238 of 366 days2012: Moderate 126 of 366 days2012: Unhealthy for Sensitive Groups 2 of 366 days2013: Good 245 of 365 days2013: Moderate 119 of 365 days2013: Unhealthy for Sensitive Groups 1 of 365 days20132014: Good 285 of 365 days2014: Moderate 80 of 365 days2015: Good 282 of 365 days2015: Moderate 83 of 365 days2016: Good 286 of 366 days2016: Moderate 80 of 366 days2017: Good 284 of 365 days2017: Moderate 80 of 365 days2017: Unhealthy for Sensitive Groups 1 of 365 days2018: Good 259 of 359 days2018: Moderate 96 of 359 days2018: Unhealthy for Sensitive Groups 4 of 359 days20182019: Good 279 of 365 days2019: Moderate 86 of 365 days2020: Good 301 of 366 days2020: Moderate 63 of 366 days2020: Unhealthy for Sensitive Groups 2 of 366 days2021: Good 280 of 365 days2021: Moderate 83 of 365 days2021: Unhealthy for Sensitive Groups 2 of 365 days2022: Good 300 of 365 days2022: Moderate 65 of 365 days2023: Good 291 of 365 days2023: Moderate 74 of 365 days20232024: Good 262 of 366 days2024: Moderate 103 of 366 days2024: Unhealthy for Sensitive Groups 1 of 366 days2025: Good 274 of 365 days2025: Moderate 90 of 365 days2025: Unhealthy for Sensitive Groups 1 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 year0501001988: 90th percentile AQI 241989: 90th percentile AQI 301990: 90th percentile AQI 421991: 90th percentile AQI 291992: 90th percentile AQI 231993: 90th percentile AQI 471994: 90th percentile AQI 541995: 90th percentile AQI 581996: 90th percentile AQI 611997: 90th percentile AQI 511998: 90th percentile AQI 711999: 90th percentile AQI 772000: 90th percentile AQI 802001: 90th percentile AQI 642002: 90th percentile AQI 772003: 90th percentile AQI 742004: 90th percentile AQI 672005: 90th percentile AQI 842006: 90th percentile AQI 842007: 90th percentile AQI 772008: 90th percentile AQI 712009: 90th percentile AQI 742010: 90th percentile AQI 642011: 90th percentile AQI 772012: 90th percentile AQI 772013: 90th percentile AQI 712014: 90th percentile AQI 612015: 90th percentile AQI 612016: 90th percentile AQI 642017: 90th percentile AQI 642018: 90th percentile AQI 712019: 90th percentile AQI 612020: 90th percentile AQI 582021: 90th percentile AQI 642022: 90th percentile AQI 612023: 90th percentile AQI 582024: 90th percentile AQI 672025: 90th percentile AQI 641988: Median AQI 161989: Median AQI 171990: Median AQI 191991: Median AQI 181992: Median AQI 151993: Median AQI 341994: Median AQI 421995: Median AQI 441996: Median AQI 441997: Median AQI 421998: Median AQI 451999: Median AQI 482000: Median AQI 452001: Median AQI 442002: Median AQI 452003: Median AQI 462004: Median AQI 452005: Median AQI 482006: Median AQI 482007: Median AQI 472008: Median AQI 462009: Median AQI 482010: Median AQI 462011: Median AQI 472012: Median AQI 472013: Median AQI 462014: Median AQI 452015: Median AQI 442016: Median AQI 442017: Median AQI 442018: Median AQI 442019: Median AQI 462020: Median AQI 442021: Median AQI 442022: Median AQI 442023: Median AQI 442024: Median AQI 452025: Median AQI 45198819931998200320082013201820232025
  • 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
Ozone36399%
Fine particles (PM2.5)21%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
20253652749010004564101Ozone
202436626210310004567101Ozone
2023365291740000445880Ozone
2022365300650000446187Ozone
20213652808320004464115Ozone
20203663016320004458126Ozone
2019365279860000466197Ozone
20183592599640004471115Ozone
20173652848010004464105Ozone
2016366286800000446497Ozone
2015365282830000446193Ozone
2014365285800000456193Ozone
201336524511910004671128Ozone
201236623812620004777105Ozone
201136522713350004777126Ozone
20103652659910004664122Ozone
200936522014320004874108Ozone
200836323612610004671101Ozone
200735922213430004777105Ozone
200636321813870004884147Ozone
2005364212142100004884126Ozone
20043642758720004567108Ozone
200335724511110004674126Ozone
200235623611910004577126Ozone
20013442578610004464105Ozone
200034821412590004580140Ozone
199934622811440004877106Ozone
19983202299100004571100Ozone
1997275247280000425184Ozone
19963622956340004461112Ozone
1995358292660000445890Ozone
1994321284370000425477Ozone
199322922090000344780Ozone
1992999900000152333PM2.5
1991959410000182958PM2.5
1990979430000194260PM2.5
1989979610000173051PM2.5
1988767600000162444PM2.5

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 1988–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem