EnviroNearby

Carlton County, Minnesota air quality history

Daily Air Quality Index summaries from EPA monitors in Carlton, Minnesota, 1988–2025.

83%
Good days in 2025
33
Median daily AQI, 2025
12
Days above 100 in 2025
355
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Carlton, Minnesota on 355 days. 294 of those days (83%) were in the Good range, and the median daily AQI was 33. 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 fine particles (PM2.5) on 202 days. Across the years with fuller monitoring, the share of Good days fell: an average of 97% in 1989–2001 versus 82% in 2023–2025.

Years with fewer than 120 monitored days (1995, 1996, 1997, 1998, 1999, 2000…) 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 11 of 12 days1988: Moderate 1 of 12 days19881989: Good 301 of 307 days1989: Moderate 6 of 307 days1990: Good 363 of 365 days1990: Moderate 2 of 365 days1991: Good 56 of 56 days1992: Good 53 of 53 days1993: Good 50 of 50 days19931994: Good 60 of 60 days1995: Good 59 of 59 days1996: Good 53 of 54 days1996: Moderate 1 of 54 days1997: Good 53 of 53 days1998: Good 53 of 53 days19981999: Good 48 of 48 days2000: Good 42 of 42 days2001: Good 208 of 221 days2001: Moderate 12 of 221 days2001: Unhealthy for Sensitive Groups 1 of 221 days2002: Good 321 of 342 days2002: Moderate 21 of 342 days2003: Good 329 of 357 days2003: Moderate 28 of 357 days20032004: Good 327 of 359 days2004: Moderate 32 of 359 days2005: Good 230 of 245 days2005: Moderate 14 of 245 days2005: Unhealthy for Sensitive Groups 1 of 245 days2006: Good 227 of 271 days2006: Moderate 44 of 271 days2007: Good 231 of 282 days2007: Moderate 51 of 282 days2008: Good 178 of 187 days2008: Moderate 9 of 187 days20082009: Good 161 of 165 days2009: Moderate 4 of 165 days2010: Good 356 of 365 days2010: Moderate 8 of 365 days2010: Unhealthy for Sensitive Groups 1 of 365 days2011: Good 207 of 207 days2012: Good 212 of 222 days2012: Moderate 9 of 222 days2012: Unhealthy for Sensitive Groups 1 of 222 days2013: Good 195 of 204 days2013: Moderate 9 of 204 days20132014: Good 226 of 230 days2014: Moderate 4 of 230 days2015: Good 238 of 275 days2015: Moderate 36 of 275 days2015: Unhealthy for Sensitive Groups 1 of 275 days2016: Good 337 of 364 days2016: Moderate 26 of 364 days2016: Unhealthy for Sensitive Groups 1 of 364 days2017: Good 334 of 365 days2017: Moderate 31 of 365 days2018: Good 319 of 354 days2018: Moderate 35 of 354 days20182019: Good 341 of 356 days2019: Moderate 15 of 356 days2020: Good 347 of 354 days2020: Moderate 7 of 354 days2021: Good 318 of 365 days2021: Moderate 43 of 365 days2021: Unhealthy for Sensitive Groups 4 of 365 days2022: Good 351 of 355 days2022: Moderate 4 of 355 days2023: Good 266 of 362 days2023: Moderate 91 of 362 days2023: Unhealthy for Sensitive Groups 4 of 362 days2023: Unhealthy 1 of 362 days20232024: Good 326 of 366 days2024: Moderate 39 of 366 days2024: Unhealthy for Sensitive Groups 1 of 366 days2025: Good 294 of 355 days2025: Moderate 49 of 355 days2025: Unhealthy for Sensitive Groups 5 of 355 days2025: Unhealthy 7 of 355 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 331989: 90th percentile AQI 301990: 90th percentile AQI 221991: 90th percentile AQI 231992: 90th percentile AQI 241993: 90th percentile AQI 221994: 90th percentile AQI 211995: 90th percentile AQI 231996: 90th percentile AQI 221997: 90th percentile AQI 281998: 90th percentile AQI 281999: 90th percentile AQI 232000: 90th percentile AQI 172001: 90th percentile AQI 442002: 90th percentile AQI 442003: 90th percentile AQI 482004: 90th percentile AQI 492005: 90th percentile AQI 492006: 90th percentile AQI 542007: 90th percentile AQI 562008: 90th percentile AQI 462009: 90th percentile AQI 472010: 90th percentile AQI 412011: 90th percentile AQI 432012: 90th percentile AQI 452013: 90th percentile AQI 462014: 90th percentile AQI 432015: 90th percentile AQI 532016: 90th percentile AQI 462017: 90th percentile AQI 482018: 90th percentile AQI 502019: 90th percentile AQI 452020: 90th percentile AQI 422021: 90th percentile AQI 542022: 90th percentile AQI 412023: 90th percentile AQI 632024: 90th percentile AQI 522025: 90th percentile AQI 621988: Median AQI 141989: Median AQI 111990: Median AQI 111991: Median AQI 131992: Median AQI 111993: Median AQI 111994: Median AQI 111995: Median AQI 111996: Median AQI 111997: Median AQI 111998: Median AQI 121999: Median AQI 122000: Median AQI 112001: Median AQI 212002: Median AQI 192003: Median AQI 192004: Median AQI 292005: Median AQI 452006: Median AQI 352007: Median AQI 332008: Median AQI 322009: Median AQI 332010: Median AQI 182011: Median AQI 322012: Median AQI 322013: Median AQI 332014: Median AQI 312015: Median AQI 372016: Median AQI 312017: Median AQI 312018: Median AQI 302019: Median AQI 282020: Median AQI 252021: Median AQI 312022: Median AQI 252023: Median AQI 382024: Median AQI 342025: Median AQI 33198819931998200320082013201820232025
  • 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
Fine particles (PM2.5)20257%
Ozone15343%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
20253552944957003362184PM2.5
20243663263910003452114PM2.5
20233622669141003863156PM2.5
202235535140000254157Ozone
20213653184340003154143Ozone
202035434770000254284Ozone
2019356341150000284580Ozone
2018354319350000305094PM2.5
2017365334310000314884PM2.5
20163643372610003146101Ozone
20152752383610003753101Ozone
201423022640000314387Ozone
201320419590000334693Ozone
2012222212910003245122Ozone
201120720700000324349Ozone
2010365356810001841101Ozone
200916516140000334784Ozone
200818717890000324674Ozone
2007282231510000335697PM2.5
2006271227440000355476PM2.5
20052452301410004549112PM2.5
2004359327320000294980PM2.5
2003357329280000194897Ozone
2002342321210000194477PM2.5
20012212081210002144129Ozone
2000424200000111744PM10
1999484800000122330PM10
1998535300000122840PM10
1997535300000112841PM10
1996545310000112255PM10
1995595900000112340PM10
1994606000000112139PM10
1993505000000112232PM10
1992535300000112432PM10
1991565600000132343PM10
199036536320000112265NO2
198930730160000113058NO2
1988121110000143371PM10

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 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