EnviroNearby

Washington County, Minnesota air quality history

Daily Air Quality Index summaries from EPA monitors in Washington, Minnesota, 1980–2025.

95%
Good days in 2025
34
Median daily AQI, 2025
0
Days above 100 in 2025
236
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Washington, Minnesota on 236 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 236 days. Across the years with fuller monitoring, the share of Good days rose: an average of 84% in 1980–1982 versus 91% in 2023–2025.

EPA did not report an AQI for every day of 2025 here (236 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.

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 99 of 143 days1980: Moderate 32 of 143 days1980: Unhealthy for Sensitive Groups 7 of 143 days1980: Unhealthy 5 of 143 days19801981: Good 162 of 171 days1981: Moderate 9 of 171 days1982: Good 109 of 123 days1982: Moderate 12 of 123 days1982: Unhealthy for Sensitive Groups 2 of 123 days1983: Good 122 of 153 days1983: Moderate 27 of 153 days1983: Unhealthy for Sensitive Groups 3 of 153 days1983: Unhealthy 1 of 153 days1984: Good 133 of 150 days1984: Moderate 14 of 150 days1984: Unhealthy for Sensitive Groups 1 of 150 days1984: Unhealthy 2 of 150 days1985: Good 127 of 153 days1985: Moderate 22 of 153 days1985: Unhealthy for Sensitive Groups 4 of 153 days19851986: Good 148 of 172 days1986: Moderate 22 of 172 days1986: Unhealthy for Sensitive Groups 2 of 172 days1987: Good 144 of 174 days1987: Moderate 29 of 174 days1987: Unhealthy for Sensitive Groups 1 of 174 days1988: Good 87 of 148 days1988: Moderate 39 of 148 days1988: Unhealthy for Sensitive Groups 16 of 148 days1988: Unhealthy 5 of 148 days1988: Very Unhealthy 1 of 148 days1989: Good 135 of 175 days1989: Moderate 35 of 175 days1989: Unhealthy for Sensitive Groups 5 of 175 days1990: Good 154 of 169 days1990: Moderate 13 of 169 days1990: Unhealthy for Sensitive Groups 2 of 169 days19901991: Good 150 of 175 days1991: Moderate 25 of 175 days1992: Good 167 of 193 days1992: Moderate 17 of 193 days1992: Unhealthy for Sensitive Groups 8 of 193 days1992: Unhealthy 1 of 193 days1993: Good 208 of 224 days1993: Moderate 14 of 224 days1993: Unhealthy for Sensitive Groups 2 of 224 days1994: Good 210 of 228 days1994: Moderate 17 of 228 days1994: Unhealthy for Sensitive Groups 1 of 228 days1995: Good 197 of 234 days1995: Moderate 27 of 234 days1995: Unhealthy for Sensitive Groups 7 of 234 days1995: Unhealthy 3 of 234 days19951996: Good 201 of 234 days1996: Moderate 29 of 234 days1996: Unhealthy for Sensitive Groups 4 of 234 days1997: Good 143 of 143 days1998: Good 289 of 347 days1998: Moderate 50 of 347 days1998: Unhealthy for Sensitive Groups 7 of 347 days1998: Unhealthy 1 of 347 days1999: Good 303 of 354 days1999: Moderate 42 of 354 days1999: Unhealthy for Sensitive Groups 9 of 354 days2000: Good 168 of 219 days2000: Moderate 47 of 219 days2000: Unhealthy for Sensitive Groups 4 of 219 days20002001: Good 172 of 221 days2001: Moderate 41 of 221 days2001: Unhealthy for Sensitive Groups 6 of 221 days2001: Unhealthy 2 of 221 days2002: Good 167 of 208 days2002: Moderate 37 of 208 days2002: Unhealthy for Sensitive Groups 3 of 208 days2002: Unhealthy 1 of 208 days2003: Good 150 of 209 days2003: Moderate 53 of 209 days2003: Unhealthy for Sensitive Groups 6 of 209 days2004: Good 190 of 210 days2004: Moderate 20 of 210 days2005: Good 152 of 198 days2005: Moderate 40 of 198 days2005: Unhealthy for Sensitive Groups 6 of 198 days20052006: Good 172 of 212 days2006: Moderate 38 of 212 days2006: Unhealthy for Sensitive Groups 2 of 212 days2007: Good 158 of 209 days2007: Moderate 45 of 209 days2007: Unhealthy for Sensitive Groups 6 of 209 days2008: Good 157 of 204 days2008: Moderate 46 of 204 days2008: Unhealthy for Sensitive Groups 1 of 204 days2009: Good 162 of 204 days2009: Moderate 42 of 204 days2010: Good 163 of 180 days2010: Moderate 16 of 180 days2010: Unhealthy for Sensitive Groups 1 of 180 days20102011: Good 180 of 192 days2011: Moderate 11 of 192 days2011: Unhealthy for Sensitive Groups 1 of 192 days2012: Good 168 of 322 days2012: Moderate 152 of 322 days2012: Unhealthy for Sensitive Groups 2 of 322 days2013: Good 202 of 365 days2013: Moderate 163 of 365 days2014: Good 229 of 365 days2014: Moderate 136 of 365 days2015: Good 203 of 365 days2015: Moderate 160 of 365 days2015: Unhealthy for Sensitive Groups 2 of 365 days20152016: Good 275 of 366 days2016: Moderate 91 of 366 days2017: Good 218 of 365 days2017: Moderate 147 of 365 days2018: Good 158 of 365 days2018: Moderate 207 of 365 days2019: Good 192 of 260 days2019: Moderate 68 of 260 days2020: Good 210 of 215 days2020: Moderate 5 of 215 days20202021: Good 205 of 227 days2021: Moderate 21 of 227 days2021: Unhealthy for Sensitive Groups 1 of 227 days2022: Good 212 of 227 days2022: Moderate 15 of 227 days2023: Good 194 of 240 days2023: Moderate 38 of 240 days2023: Unhealthy for Sensitive Groups 8 of 240 days2024: Good 241 of 246 days2024: Moderate 5 of 246 days2025: Good 224 of 236 days2025: Moderate 12 of 236 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 year0501001501980: 90th percentile AQI 971981: 90th percentile AQI 451982: 90th percentile AQI 511983: 90th percentile AQI 771984: 90th percentile AQI 511985: 90th percentile AQI 611986: 90th percentile AQI 641987: 90th percentile AQI 641988: 90th percentile AQI 1121989: 90th percentile AQI 711990: 90th percentile AQI 501991: 90th percentile AQI 581992: 90th percentile AQI 641993: 90th percentile AQI 471994: 90th percentile AQI 491995: 90th percentile AQI 671996: 90th percentile AQI 541997: 90th percentile AQI 371998: 90th percentile AQI 641999: 90th percentile AQI 642000: 90th percentile AQI 752001: 90th percentile AQI 672002: 90th percentile AQI 772003: 90th percentile AQI 842004: 90th percentile AQI 502005: 90th percentile AQI 672006: 90th percentile AQI 612007: 90th percentile AQI 672008: 90th percentile AQI 632009: 90th percentile AQI 602010: 90th percentile AQI 502011: 90th percentile AQI 482012: 90th percentile AQI 652013: 90th percentile AQI 662014: 90th percentile AQI 662015: 90th percentile AQI 622016: 90th percentile AQI 602017: 90th percentile AQI 642018: 90th percentile AQI 682019: 90th percentile AQI 642020: 90th percentile AQI 442021: 90th percentile AQI 492022: 90th percentile AQI 482023: 90th percentile AQI 772024: 90th percentile AQI 442025: 90th percentile AQI 461980: Median AQI 441981: Median AQI 311982: Median AQI 311983: Median AQI 411984: Median AQI 371985: Median AQI 391986: Median AQI 371987: Median AQI 371988: Median AQI 461989: Median AQI 421990: Median AQI 391991: Median AQI 361992: Median AQI 341993: Median AQI 321994: Median AQI 351995: Median AQI 381996: Median AQI 381997: Median AQI 261998: Median AQI 361999: Median AQI 352000: Median AQI 392001: Median AQI 402002: Median AQI 402003: Median AQI 432004: Median AQI 362005: Median AQI 402006: Median AQI 402007: Median AQI 402008: Median AQI 422009: Median AQI 412010: Median AQI 402011: Median AQI 372012: Median AQI 492013: Median AQI 472014: Median AQI 442015: Median AQI 462016: Median AQI 362017: Median AQI 462018: Median AQI 532019: Median AQI 372020: Median AQI 332021: Median AQI 352022: Median AQI 362023: Median AQI 422024: Median AQI 352025: Median AQI 341980198519901995200020052010201520202025
  • 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
Ozone236100%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
2025236224120000344684Ozone
202424624150000354458Ozone
20232401943880004277140Ozone
2022227212150000364890Ozone
20212272052110003549119Ozone
202021521050000334477Ozone
2019260192680000376487Ozone
201836515820700005368100PM2.5
20173652181470000466497PM2.5
2016366275910000366089Ozone
201536520316020004662122PM2.5
20143652291360000446698PM2.5
20133652021630000476698PM2.5
201232216815220004965107PM2.5
20111921801110003748129Ozone
20101801631610004050105Ozone
2009204162420000416093Ozone
20082041574610004263130Ozone
20072091584560004067135Ozone
20062121723820004061133Ozone
20051981524060004067136Ozone
2004210190200000365093Ozone
20032091505360004384133Ozone
20022081673731004077154Ozone
20012211724162004067169Ozone
20002191684740003975122Ozone
19993543034290003564140Ozone
19983472895071003664161Ozone
199714314300000263748Ozone
19962342012940003854150Ozone
19952341972773003867177Ozone
19942282101710003549122Ozone
19932242081420003247112Ozone
19921931671781003464169Ozone
1991175150250000365893Ozone
19901691541320003950119Ozone
19891751353550004271126Ozone
198814887391651046112212Ozone
19871741442910003764101Ozone
19861721482220003764126Ozone
19851531272240003961136Ozone
19841501331412003751179Ozone
19831531222731004177164Ozone
19821231091220003151143Ozone
198117116290000314584Ozone
1980143993275004497185Ozone

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 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