EnviroNearby

Mesa County, Colorado air quality history

Daily Air Quality Index summaries from EPA monitors in Mesa, Colorado, 1980–2025.

65%
Good days in 2025
46
Median daily AQI, 2025
0
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 Mesa, Colorado on 365 days. 238 of those days (65%) were in the Good range, and the median daily AQI was 46. 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 276 days. Across the years with fuller monitoring, the share of Good days fell: an average of 90% in 1980–1982 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%1980: Good 297 of 315 days1980: Moderate 18 of 315 days19801981: Good 217 of 263 days1981: Moderate 46 of 263 days1982: Good 337 of 360 days1982: Moderate 23 of 360 days1983: Good 299 of 324 days1983: Moderate 23 of 324 days1983: Unhealthy for Sensitive Groups 1 of 324 days1983: Very Unhealthy 1 of 324 days1984: Good 290 of 311 days1984: Moderate 21 of 311 days1985: Good 318 of 331 days1985: Moderate 13 of 331 days19851986: Good 283 of 364 days1986: Moderate 77 of 364 days1986: Unhealthy for Sensitive Groups 4 of 364 days1987: Good 237 of 365 days1987: Moderate 126 of 365 days1987: Unhealthy for Sensitive Groups 2 of 365 days1988: Good 219 of 251 days1988: Moderate 32 of 251 days1989: Good 289 of 337 days1989: Moderate 48 of 337 days1990: Good 336 of 356 days1990: Moderate 20 of 356 days19901991: Good 252 of 336 days1991: Moderate 84 of 336 days1992: Good 263 of 366 days1992: Moderate 103 of 366 days1993: Good 337 of 365 days1993: Moderate 27 of 365 days1993: Unhealthy for Sensitive Groups 1 of 365 days1994: Good 339 of 365 days1994: Moderate 26 of 365 days1995: Good 340 of 365 days1995: Moderate 25 of 365 days19951996: Good 345 of 366 days1996: Moderate 21 of 366 days1997: Good 359 of 365 days1997: Moderate 6 of 365 days1998: Good 353 of 365 days1998: Moderate 12 of 365 days1999: Good 342 of 365 days1999: Moderate 23 of 365 days2000: Good 334 of 366 days2000: Moderate 32 of 366 days20002001: Good 332 of 365 days2001: Moderate 33 of 365 days2002: Good 312 of 365 days2002: Moderate 53 of 365 days2003: Good 305 of 359 days2003: Moderate 53 of 359 days2003: Unhealthy for Sensitive Groups 1 of 359 days2004: Good 285 of 355 days2004: Moderate 69 of 355 days2004: Unhealthy for Sensitive Groups 1 of 355 days2005: Good 299 of 365 days2005: Moderate 65 of 365 days2005: Unhealthy for Sensitive Groups 1 of 365 days20052006: Good 283 of 365 days2006: Moderate 80 of 365 days2006: Unhealthy for Sensitive Groups 1 of 365 days2006: Unhealthy 1 of 365 days2007: Good 226 of 365 days2007: Moderate 137 of 365 days2007: Unhealthy for Sensitive Groups 2 of 365 days2008: Good 190 of 366 days2008: Moderate 173 of 366 days2008: Unhealthy for Sensitive Groups 3 of 366 days2009: Good 217 of 365 days2009: Moderate 142 of 365 days2009: Unhealthy for Sensitive Groups 5 of 365 days2009: Unhealthy 1 of 365 days2010: Good 217 of 365 days2010: Moderate 142 of 365 days2010: Unhealthy for Sensitive Groups 6 of 365 days20102011: Good 191 of 365 days2011: Moderate 164 of 365 days2011: Unhealthy for Sensitive Groups 10 of 365 days2012: Good 190 of 366 days2012: Moderate 165 of 366 days2012: Unhealthy for Sensitive Groups 11 of 366 days2013: Good 225 of 365 days2013: Moderate 136 of 365 days2013: Unhealthy for Sensitive Groups 4 of 365 days2014: Good 216 of 365 days2014: Moderate 148 of 365 days2014: Unhealthy for Sensitive Groups 1 of 365 days2015: Good 225 of 365 days2015: Moderate 137 of 365 days2015: Unhealthy for Sensitive Groups 3 of 365 days20152016: Good 245 of 366 days2016: Moderate 120 of 366 days2016: Unhealthy for Sensitive Groups 1 of 366 days2017: Good 213 of 365 days2017: Moderate 151 of 365 days2017: Unhealthy for Sensitive Groups 1 of 365 days2018: Good 193 of 365 days2018: Moderate 167 of 365 days2018: Unhealthy for Sensitive Groups 5 of 365 days2019: Good 238 of 364 days2019: Moderate 125 of 364 days2019: Unhealthy for Sensitive Groups 1 of 364 days2020: Good 262 of 366 days2020: Moderate 101 of 366 days2020: Unhealthy for Sensitive Groups 3 of 366 days20202021: Good 247 of 365 days2021: Moderate 116 of 365 days2021: Unhealthy for Sensitive Groups 2 of 365 days2022: Good 282 of 365 days2022: Moderate 82 of 365 days2022: Unhealthy for Sensitive Groups 1 of 365 days2023: Good 246 of 365 days2023: Moderate 119 of 365 days2024: Good 215 of 366 days2024: Moderate 144 of 366 days2024: Unhealthy for Sensitive Groups 7 of 366 days2025: Good 238 of 365 days2025: Moderate 127 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 year0501001980: 90th percentile AQI 471981: 90th percentile AQI 601982: 90th percentile AQI 471983: 90th percentile AQI 441984: 90th percentile AQI 441985: 90th percentile AQI 401986: 90th percentile AQI 631987: 90th percentile AQI 711988: 90th percentile AQI 521989: 90th percentile AQI 541990: 90th percentile AQI 481991: 90th percentile AQI 631992: 90th percentile AQI 611993: 90th percentile AQI 491994: 90th percentile AQI 481995: 90th percentile AQI 481996: 90th percentile AQI 451997: 90th percentile AQI 411998: 90th percentile AQI 431999: 90th percentile AQI 462000: 90th percentile AQI 472001: 90th percentile AQI 482002: 90th percentile AQI 562003: 90th percentile AQI 552004: 90th percentile AQI 572005: 90th percentile AQI 552006: 90th percentile AQI 572007: 90th percentile AQI 662008: 90th percentile AQI 742009: 90th percentile AQI 712010: 90th percentile AQI 742011: 90th percentile AQI 802012: 90th percentile AQI 872013: 90th percentile AQI 712014: 90th percentile AQI 672015: 90th percentile AQI 702016: 90th percentile AQI 672017: 90th percentile AQI 672018: 90th percentile AQI 802019: 90th percentile AQI 672020: 90th percentile AQI 642021: 90th percentile AQI 652022: 90th percentile AQI 582023: 90th percentile AQI 642024: 90th percentile AQI 772025: 90th percentile AQI 641980: Median AQI 181981: Median AQI 231982: Median AQI 181983: Median AQI 151984: Median AQI 171985: Median AQI 151986: Median AQI 421987: Median AQI 471988: Median AQI 411989: Median AQI 421990: Median AQI 371991: Median AQI 441992: Median AQI 431993: Median AQI 331994: Median AQI 321995: Median AQI 311996: Median AQI 311997: Median AQI 281998: Median AQI 271999: Median AQI 272000: Median AQI 262001: Median AQI 262002: Median AQI 292003: Median AQI 262004: Median AQI 252005: Median AQI 312006: Median AQI 342007: Median AQI 462008: Median AQI 502009: Median AQI 482010: Median AQI 482011: Median AQI 502012: Median AQI 502013: Median AQI 472014: Median AQI 482015: Median AQI 482016: Median AQI 472017: Median AQI 482018: Median AQI 492019: Median AQI 472020: Median AQI 442021: Median AQI 462022: Median AQI 442023: Median AQI 462024: Median AQI 482025: Median AQI 461980198519901995200020052010201520202025
  • 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
Ozone27676%
Fine particles (PM2.5)8924%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
20253652381270000466497Ozone
202436621514470004877136Ozone
20233652461190000466490Ozone
20223652828210004458108Ozone
202136524711620004665139Ozone
202036626210130004464108Ozone
201936423812510004767101Ozone
201836519316750004980150Ozone
201736521315110004867101Ozone
201636624512010004767102Ozone
201536522513730004870105Ozone
201436521614810004867101Ozone
201336522513640004771117Ozone
2012366190165110005087122Ozone
2011365191164100005080119Ozone
201036521714260004874120Ozone
200936521714251004871154Ozone
200836619017330005074122Ozone
200736522613720004666114PM10
20063652838011003457173PM10
20053652996510003155122PM10
20043552856910002557117CO
20033593055310002655140PM10
2002365312530000295678PM10
2001365332330000264879CO
2000366334320000264785CO
1999365342230000274695CO
1998365353120000274367CO
199736535960000284170CO
1996366345210000314581CO
1995365340250000314860CO
1994365339260000324881CO
19933653372710003349136CO
19923662631030000436193CO
1991336252840000446397Ozone
1990356336200000374877Ozone
1989337289480000425480Ozone
1988251219320000415290Ozone
198736523712620004771105Ozone
19863642837740004263126Ozone
1985331318130000154069CO
1984311290210000174471CO
19833242992310101544226CO
1982360337230000184783CO
1981263217460000236090CO
1980315297180000184767CO

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 1980–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem