EnviroNearby

Douglas County, Colorado air quality history

Daily Air Quality Index summaries from EPA monitors in Douglas, Colorado, 1989–2025.

68%
Good days in 2025
46
Median daily AQI, 2025
7
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 Douglas, Colorado on 365 days. 247 of those days (68%) 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 318 days. Across the years with fuller monitoring, the share of Good days fell: an average of 99% in 1990–1992 versus 60% in 2023–2025.

Years with fewer than 120 monitored days (1989, 1994) 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%1989: Good 9 of 9 days19891990: Good 220 of 221 days1990: Moderate 1 of 221 days1991: Good 345 of 350 days1991: Moderate 5 of 350 days1992: Good 194 of 195 days1992: Moderate 1 of 195 days1993: Good 120 of 162 days1993: Moderate 37 of 162 days1993: Unhealthy for Sensitive Groups 4 of 162 days1993: Unhealthy 1 of 162 days1994: Good 52 of 52 days19941995: Good 114 of 183 days1995: Moderate 60 of 183 days1995: Unhealthy for Sensitive Groups 9 of 183 days1996: Good 131 of 248 days1996: Moderate 92 of 248 days1996: Unhealthy for Sensitive Groups 24 of 248 days1996: Unhealthy 1 of 248 days1997: Good 131 of 220 days1997: Moderate 82 of 220 days1997: Unhealthy for Sensitive Groups 7 of 220 days1998: Good 123 of 222 days1998: Moderate 78 of 222 days1998: Unhealthy for Sensitive Groups 18 of 222 days1998: Unhealthy 3 of 222 days1999: Good 111 of 181 days1999: Moderate 61 of 181 days1999: Unhealthy for Sensitive Groups 9 of 181 days19992000: Good 137 of 234 days2000: Moderate 77 of 234 days2000: Unhealthy for Sensitive Groups 20 of 234 days2001: Good 132 of 236 days2001: Moderate 91 of 236 days2001: Unhealthy for Sensitive Groups 12 of 236 days2001: Unhealthy 1 of 236 days2002: Good 104 of 214 days2002: Moderate 85 of 214 days2002: Unhealthy for Sensitive Groups 23 of 214 days2002: Unhealthy 2 of 214 days2003: Good 105 of 198 days2003: Moderate 62 of 198 days2003: Unhealthy for Sensitive Groups 24 of 198 days2003: Unhealthy 5 of 198 days2003: Very Unhealthy 2 of 198 days2004: Good 212 of 286 days2004: Moderate 64 of 286 days2004: Unhealthy for Sensitive Groups 10 of 286 days20042005: Good 247 of 362 days2005: Moderate 87 of 362 days2005: Unhealthy for Sensitive Groups 27 of 362 days2005: Unhealthy 1 of 362 days2006: Good 206 of 360 days2006: Moderate 113 of 360 days2006: Unhealthy for Sensitive Groups 37 of 360 days2006: Unhealthy 4 of 360 days2007: Good 220 of 359 days2007: Moderate 115 of 359 days2007: Unhealthy for Sensitive Groups 23 of 359 days2007: Unhealthy 1 of 359 days2008: Good 228 of 364 days2008: Moderate 119 of 364 days2008: Unhealthy for Sensitive Groups 16 of 364 days2008: Unhealthy 1 of 364 days2009: Good 264 of 363 days2009: Moderate 92 of 363 days2009: Unhealthy for Sensitive Groups 7 of 363 days20092010: Good 229 of 354 days2010: Moderate 112 of 354 days2010: Unhealthy for Sensitive Groups 13 of 354 days2011: Good 222 of 360 days2011: Moderate 116 of 360 days2011: Unhealthy for Sensitive Groups 21 of 360 days2011: Unhealthy 1 of 360 days2012: Good 191 of 348 days2012: Moderate 121 of 348 days2012: Unhealthy for Sensitive Groups 32 of 348 days2012: Unhealthy 4 of 348 days2013: Good 238 of 364 days2013: Moderate 101 of 364 days2013: Unhealthy for Sensitive Groups 24 of 364 days2013: Unhealthy 1 of 364 days2014: Good 238 of 363 days2014: Moderate 116 of 363 days2014: Unhealthy for Sensitive Groups 9 of 363 days20142015: Good 248 of 362 days2015: Moderate 103 of 362 days2015: Unhealthy for Sensitive Groups 9 of 362 days2015: Unhealthy 2 of 362 days2016: Good 251 of 362 days2016: Moderate 95 of 362 days2016: Unhealthy for Sensitive Groups 15 of 362 days2016: Unhealthy 1 of 362 days2017: Good 194 of 363 days2017: Moderate 152 of 363 days2017: Unhealthy for Sensitive Groups 16 of 363 days2017: Unhealthy 1 of 363 days2018: Good 194 of 364 days2018: Moderate 143 of 364 days2018: Unhealthy for Sensitive Groups 24 of 364 days2018: Unhealthy 3 of 364 days2019: Good 220 of 361 days2019: Moderate 130 of 361 days2019: Unhealthy for Sensitive Groups 10 of 361 days2019: Unhealthy 1 of 361 days20192020: Good 221 of 361 days2020: Moderate 123 of 361 days2020: Unhealthy for Sensitive Groups 14 of 361 days2020: Unhealthy 3 of 361 days2021: Good 195 of 358 days2021: Moderate 121 of 358 days2021: Unhealthy for Sensitive Groups 34 of 358 days2021: Unhealthy 8 of 358 days2022: Good 242 of 365 days2022: Moderate 105 of 365 days2022: Unhealthy for Sensitive Groups 17 of 365 days2022: Unhealthy 1 of 365 days2023: Good 200 of 364 days2023: Moderate 149 of 364 days2023: Unhealthy for Sensitive Groups 14 of 364 days2023: Unhealthy 1 of 364 days2024: Good 208 of 363 days2024: Moderate 130 of 363 days2024: Unhealthy for Sensitive Groups 21 of 363 days2024: Unhealthy 4 of 363 days20242025: Good 247 of 365 days2025: Moderate 111 of 365 days2025: Unhealthy for Sensitive Groups 7 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 year0501001501989: 90th percentile AQI 451990: 90th percentile AQI 301991: 90th percentile AQI 271992: 90th percentile AQI 241993: 90th percentile AQI 671994: 90th percentile AQI 221995: 90th percentile AQI 901996: 90th percentile AQI 1011997: 90th percentile AQI 871998: 90th percentile AQI 931999: 90th percentile AQI 842000: 90th percentile AQI 1002001: 90th percentile AQI 842002: 90th percentile AQI 1012003: 90th percentile AQI 1222004: 90th percentile AQI 742005: 90th percentile AQI 932006: 90th percentile AQI 1052007: 90th percentile AQI 972008: 90th percentile AQI 902009: 90th percentile AQI 742010: 90th percentile AQI 802011: 90th percentile AQI 932012: 90th percentile AQI 1012013: 90th percentile AQI 902014: 90th percentile AQI 742015: 90th percentile AQI 772016: 90th percentile AQI 802017: 90th percentile AQI 902018: 90th percentile AQI 972019: 90th percentile AQI 792020: 90th percentile AQI 802021: 90th percentile AQI 1082022: 90th percentile AQI 872023: 90th percentile AQI 842024: 90th percentile AQI 932025: 90th percentile AQI 711989: Median AQI 221990: Median AQI 161991: Median AQI 151992: Median AQI 171993: Median AQI 441994: Median AQI 141995: Median AQI 471996: Median AQI 491997: Median AQI 481998: Median AQI 481999: Median AQI 482000: Median AQI 492001: Median AQI 482002: Median AQI 512003: Median AQI 502004: Median AQI 442005: Median AQI 442006: Median AQI 452007: Median AQI 442008: Median AQI 462009: Median AQI 442010: Median AQI 462011: Median AQI 462012: Median AQI 482013: Median AQI 442014: Median AQI 442015: Median AQI 442016: Median AQI 442017: Median AQI 492018: Median AQI 492019: Median AQI 472020: Median AQI 472021: Median AQI 482022: Median AQI 462023: Median AQI 492024: Median AQI 482025: Median AQI 46198919941999200420092014201920242025
  • 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
Ozone31887%
Fine particles (PM2.5)4713%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
202536524711170004671122Ozone
2024363208130214004893166Ozone
2023364200149141004984177Ozone
2022365242105171004687169Ozone
20213581951213480048108177Ozone
2020361221123143004780159Ozone
2019361220130101004779154Ozone
2018364194143243004997156Ozone
2017363194152161004990156Ozone
201636225195151004480151Ozone
201536224810392004477169Ozone
201436323811690004474124Ozone
2013364238101241004490151Ozone
20123481911213240048101182Ozone
2011360222116211004693185Ozone
2010354229112130004680136Ozone
20093632649270004474150Ozone
2008364228119161004690161Ozone
2007359220115231004497154Ozone
20063602061133740045105166Ozone
200536224787271004493164Ozone
200428621264100004474122Ozone
2003198105622452050122213Ozone
2002214104852320051101172Ozone
200123613291121004884159Ozone
2000234137772000049100143Ozone
19991811116190004884129Ozone
199822212378183004893179Ozone
19972201318270004887129Ozone
1996248131922410049101156Ozone
19951831146090004790126Ozone
1994525200000142231PM10
19931621203741004467166Ozone
199219519410000172461PM10
199135034550000152771PM10
199022122010000163054PM10
19899900000224545PM10

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 1989–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem