EnviroNearby

Ashland County, Wisconsin air quality history

Daily Air Quality Index summaries from EPA monitors in Ashland, Wisconsin, 2001–2025.

82%
Good days in 2025
36
Median daily AQI, 2025
13
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 Ashland, Wisconsin on 365 days. 298 of those days (82%) were in the Good range, and the median daily AQI was 36. That median is about the same as the typical monitored county in Wisconsin (median 38 across 29 counties), and lower than the typical monitored U.S. county (40). The main pollutant was ozone on 229 days. Across the years with fuller monitoring, the share of Good days fell: an average of 93% in 2004–2006 versus 82% in 2023–2025.

Years with fewer than 120 monitored days (2001, 2002, 2003) 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%2001: Good 34 of 34 days20012002: Good 54 of 58 days2002: Moderate 4 of 58 days2003: Good 52 of 62 days2003: Moderate 10 of 62 days20032004: Good 164 of 176 days2004: Moderate 12 of 176 days2005: Good 330 of 359 days2005: Moderate 29 of 359 days20052006: Good 335 of 362 days2006: Moderate 27 of 362 days2007: Good 334 of 363 days2007: Moderate 28 of 363 days2007: Unhealthy for Sensitive Groups 1 of 363 days20072008: Good 338 of 359 days2008: Moderate 20 of 359 days2008: Unhealthy for Sensitive Groups 1 of 359 days2009: Good 312 of 330 days2009: Moderate 18 of 330 days20092010: Good 337 of 363 days2010: Moderate 26 of 363 days2011: Good 322 of 337 days2011: Moderate 15 of 337 days20112012: Good 327 of 352 days2012: Moderate 24 of 352 days2012: Unhealthy for Sensitive Groups 1 of 352 days2013: Good 345 of 361 days2013: Moderate 16 of 361 days20132014: Good 340 of 354 days2014: Moderate 14 of 354 days2015: Good 347 of 360 days2015: Moderate 13 of 360 days20152016: Good 342 of 358 days2016: Moderate 16 of 358 days2017: Good 357 of 362 days2017: Moderate 5 of 362 days20172018: Good 324 of 360 days2018: Moderate 36 of 360 days2019: Good 332 of 364 days2019: Moderate 32 of 364 days20192020: Good 336 of 366 days2020: Moderate 30 of 366 days2021: Good 282 of 365 days2021: Moderate 79 of 365 days2021: Unhealthy for Sensitive Groups 3 of 365 days2021: Unhealthy 1 of 365 days20212022: Good 334 of 364 days2022: Moderate 30 of 364 days2023: Good 272 of 365 days2023: Moderate 87 of 365 days2023: Unhealthy for Sensitive Groups 6 of 365 days20232024: Good 331 of 364 days2024: Moderate 32 of 364 days2024: Unhealthy for Sensitive Groups 1 of 364 days2025: Good 298 of 365 days2025: Moderate 54 of 365 days2025: Unhealthy for Sensitive Groups 5 of 365 days2025: Unhealthy 8 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 year0501002001: 90th percentile AQI 192002: 90th percentile AQI 382003: 90th percentile AQI 582004: 90th percentile AQI 472005: 90th percentile AQI 492006: 90th percentile AQI 482007: 90th percentile AQI 492008: 90th percentile AQI 472009: 90th percentile AQI 452010: 90th percentile AQI 462011: 90th percentile AQI 452012: 90th percentile AQI 472013: 90th percentile AQI 452014: 90th percentile AQI 442015: 90th percentile AQI 442016: 90th percentile AQI 422017: 90th percentile AQI 442018: 90th percentile AQI 512019: 90th percentile AQI 502020: 90th percentile AQI 482021: 90th percentile AQI 582022: 90th percentile AQI 482023: 90th percentile AQI 642024: 90th percentile AQI 492025: 90th percentile AQI 622001: Median AQI 112002: Median AQI 172003: Median AQI 292004: Median AQI 302005: Median AQI 332006: Median AQI 342007: Median AQI 322008: Median AQI 322009: Median AQI 312010: Median AQI 342011: Median AQI 332012: Median AQI 322013: Median AQI 332014: Median AQI 322015: Median AQI 332016: Median AQI 322017: Median AQI 332018: Median AQI 362019: Median AQI 352020: Median AQI 342021: Median AQI 372022: Median AQI 362023: Median AQI 402024: Median AQI 342025: Median AQI 362001200320052007200920112013201520172019202120232025
  • 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
Ozone22963%
Fine particles (PM2.5)13637%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
20253652985458003662188Ozone
20243643313210003449101Ozone
20233652728760004064115Ozone
2022364334300000364874Ozone
20213652827931003758160Ozone
2020366336300000344872Ozone
2019364332320000355081Ozone
2018360324360000365184Ozone
201736235750000334487Ozone
2016358342160000324280Ozone
2015360347130000334477Ozone
2014354340140000324484Ozone
2013361345160000334580Ozone
20123523272410003247112Ozone
2011337322150000334571Ozone
2010363337260000344671Ozone
2009330312180000314577Ozone
20083593382010003247127Ozone
20073633342810003249105Ozone
2006362335270000344887Ozone
20053593302900003349100Ozone
2004176164120000304771Ozone
20036252100000295873PM2.5
2002585440000173866PM10
2001343400000111940PM10

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 Wisconsin with a similar median AQI in 2025

All monitored counties in Wisconsin

Source: U.S. EPA AirData, “Annual AQI by County” files for 2001–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem