EnviroNearby

Mille Lacs County, Minnesota air quality history

Daily Air Quality Index summaries from EPA monitors in Mille Lacs, Minnesota, 1997–2025.

95%
Good days in 2025
34
Median daily AQI, 2025
0
Days above 100 in 2025
235
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Mille Lacs, Minnesota on 235 days. 224 of those days (95%) were in the Good range, and the median daily AQI was 34. That median is lower than the typical monitored county in Minnesota (median 37 across 21 counties), and lower than the typical monitored U.S. county (40). The main pollutant was ozone on 235 days. Across the years with fuller monitoring, the share of Good days rose: an average of 79% in 1999–2001 versus 95% in 2022–2025.

EPA did not report an AQI for every day of 2025 here (235 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.

Years with fewer than 120 monitored days (1997, 1998, 2024) 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%1997: Good 15 of 15 days19971998: Good 50 of 51 days1998: Moderate 1 of 51 days1999: Good 199 of 246 days1999: Moderate 37 of 246 days1999: Unhealthy for Sensitive Groups 9 of 246 days1999: Unhealthy 1 of 246 days2000: Good 183 of 236 days2000: Moderate 52 of 236 days2000: Unhealthy for Sensitive Groups 1 of 236 days2001: Good 171 of 219 days2001: Moderate 41 of 219 days2001: Unhealthy for Sensitive Groups 7 of 219 days2002: Good 176 of 235 days2002: Moderate 56 of 235 days2002: Unhealthy for Sensitive Groups 3 of 235 days20022003: Good 178 of 238 days2003: Moderate 56 of 238 days2003: Unhealthy for Sensitive Groups 2 of 238 days2003: Unhealthy 2 of 238 days2004: Good 200 of 242 days2004: Moderate 42 of 242 days2005: Good 181 of 238 days2005: Moderate 51 of 238 days2005: Unhealthy for Sensitive Groups 4 of 238 days2005: Unhealthy 2 of 238 days2006: Good 176 of 232 days2006: Moderate 54 of 232 days2006: Unhealthy for Sensitive Groups 2 of 232 days2007: Good 192 of 231 days2007: Moderate 35 of 231 days2007: Unhealthy for Sensitive Groups 4 of 231 days20072008: Good 199 of 236 days2008: Moderate 36 of 236 days2008: Unhealthy for Sensitive Groups 1 of 236 days2009: Good 204 of 233 days2009: Moderate 29 of 233 days2010: Good 189 of 196 days2010: Moderate 6 of 196 days2010: Unhealthy for Sensitive Groups 1 of 196 days2011: Good 200 of 207 days2011: Moderate 6 of 207 days2011: Unhealthy for Sensitive Groups 1 of 207 days2012: Good 211 of 221 days2012: Moderate 10 of 221 days20122013: Good 205 of 213 days2013: Moderate 8 of 213 days2014: Good 215 of 220 days2014: Moderate 5 of 220 days2015: Good 214 of 223 days2015: Moderate 9 of 223 days2016: Good 204 of 211 days2016: Moderate 7 of 211 days2017: Good 231 of 240 days2017: Moderate 9 of 240 days20172018: Good 114 of 126 days2018: Moderate 12 of 126 days2019: Good 239 of 247 days2019: Moderate 8 of 247 days2020: Good 240 of 245 days2020: Moderate 5 of 245 days2021: Good 232 of 245 days2021: Moderate 13 of 245 days2022: Good 151 of 151 days20222023: Good 213 of 237 days2023: Moderate 19 of 237 days2023: Unhealthy for Sensitive Groups 5 of 237 days2024: Good 73 of 74 days2024: Moderate 1 of 74 days2025: Good 224 of 235 days2025: Moderate 11 of 235 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 year0501001997: 90th percentile AQI 191998: 90th percentile AQI 271999: 90th percentile AQI 772000: 90th percentile AQI 712001: 90th percentile AQI 662002: 90th percentile AQI 712003: 90th percentile AQI 672004: 90th percentile AQI 582005: 90th percentile AQI 672006: 90th percentile AQI 672007: 90th percentile AQI 582008: 90th percentile AQI 552009: 90th percentile AQI 542010: 90th percentile AQI 442011: 90th percentile AQI 442012: 90th percentile AQI 472013: 90th percentile AQI 462014: 90th percentile AQI 442015: 90th percentile AQI 462016: 90th percentile AQI 412017: 90th percentile AQI 462018: 90th percentile AQI 492019: 90th percentile AQI 442020: 90th percentile AQI 442021: 90th percentile AQI 472022: 90th percentile AQI 432023: 90th percentile AQI 512024: 90th percentile AQI 422025: 90th percentile AQI 461997: Median AQI 61998: Median AQI 91999: Median AQI 372000: Median AQI 372001: Median AQI 382002: Median AQI 412003: Median AQI 422004: Median AQI 372005: Median AQI 402006: Median AQI 412007: Median AQI 362008: Median AQI 362009: Median AQI 332010: Median AQI 332011: Median AQI 332012: Median AQI 332013: Median AQI 342014: Median AQI 312015: Median AQI 332016: Median AQI 302017: Median AQI 332018: Median AQI 302019: Median AQI 322020: Median AQI 332021: Median AQI 362022: Median AQI 352023: Median AQI 402024: Median AQI 362025: Median AQI 341997200220072012201720222025
  • 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
Ozone235100%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
2025235224110000344697Ozone
2024747310000364267Ozone
20232372131950004051136Ozone
202215115100000354348Ozone
2021245232130000364771Ozone
202024524050000334487Ozone
201924723980000324490Ozone
2018126114120000304974Ozone
201724023190000334693Ozone
201621120470000304177Ozone
201522321490000334687Ozone
201422021550000314477Ozone
201321320580000344674Ozone
2012221211100000334793Ozone
2011207200610003344101Ozone
2010196189610003344115Ozone
2009233204290000335492Ozone
20082361993610003655106Ozone
20072311923540003658136Ozone
20062321765420004167140Ozone
20052381815142004067151Ozone
2004242200420000375893Ozone
20032381785622004267156Ozone
20022351765630004171119Ozone
20012191714170003866140Ozone
20002361835210003771140Ozone
19992461993791003777159Ozone
199851501000092753PM10
199715150000061937PM10

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 Minnesota with a similar median AQI in 2025

All monitored counties in Minnesota

Source: U.S. EPA AirData, “Annual AQI by County” files for 1997–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem