EnviroNearby

Eau Claire County, Wisconsin air quality history

Daily Air Quality Index summaries from EPA monitors in Eau Claire, Wisconsin, 1980–2025.

74%
Good days in 2025
38
Median daily AQI, 2025
11
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 Eau Claire, Wisconsin on 365 days. 269 of those days (74%) were in the Good range, and the median daily AQI was 38. That median is about the same as the typical monitored county in Wisconsin (median 38 across 29 counties), and about the same as the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 269 days. Across the years with fuller monitoring, the share of Good days fell: an average of 85% in 1980–2012 versus 71% in 2023–2025.

Years with fewer than 120 monitored days (2002, 2003, 2004, 2005, 2009, 2010) 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%1980: Good 321 of 321 days19802002: Good 49 of 49 days2003: Good 54 of 54 days20032004: Good 56 of 56 days2005: Good 41 of 41 days20052009: Good 31 of 39 days2009: Moderate 8 of 39 days2010: Good 26 of 42 days2010: Moderate 16 of 42 days20102011: Good 189 of 224 days2011: Moderate 35 of 224 days2012: Good 210 of 303 days2012: Moderate 91 of 303 days2012: Unhealthy for Sensitive Groups 2 of 303 days20122013: Good 255 of 358 days2013: Moderate 103 of 358 days2014: Good 279 of 354 days2014: Moderate 75 of 354 days20142015: Good 303 of 358 days2015: Moderate 54 of 358 days2015: Unhealthy for Sensitive Groups 1 of 358 days2016: Good 268 of 359 days2016: Moderate 91 of 359 days20162017: Good 276 of 365 days2017: Moderate 89 of 365 days2018: Good 244 of 365 days2018: Moderate 120 of 365 days2018: Unhealthy for Sensitive Groups 1 of 365 days20182019: Good 268 of 363 days2019: Moderate 95 of 363 days2020: Good 256 of 366 days2020: Moderate 110 of 366 days20202021: Good 212 of 362 days2021: Moderate 145 of 362 days2021: Unhealthy for Sensitive Groups 4 of 362 days2021: Unhealthy 1 of 362 days2022: Good 268 of 365 days2022: Moderate 97 of 365 days20222023: Good 210 of 365 days2023: Moderate 137 of 365 days2023: Unhealthy for Sensitive Groups 13 of 365 days2023: Unhealthy 5 of 365 days2024: Good 299 of 366 days2024: Moderate 66 of 366 days2024: Unhealthy for Sensitive Groups 1 of 366 days20242025: Good 269 of 365 days2025: Moderate 85 of 365 days2025: Unhealthy for Sensitive Groups 6 of 365 days2025: Unhealthy 5 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 year0501001980: 90th percentile AQI 252002: 90th percentile AQI 282003: 90th percentile AQI 272004: 90th percentile AQI 222005: 90th percentile AQI 272009: 90th percentile AQI 652010: 90th percentile AQI 742011: 90th percentile AQI 562012: 90th percentile AQI 672013: 90th percentile AQI 612014: 90th percentile AQI 582015: 90th percentile AQI 542016: 90th percentile AQI 572017: 90th percentile AQI 572018: 90th percentile AQI 652019: 90th percentile AQI 602020: 90th percentile AQI 592021: 90th percentile AQI 672022: 90th percentile AQI 582023: 90th percentile AQI 782024: 90th percentile AQI 562025: 90th percentile AQI 621980: Median AQI 122002: Median AQI 132003: Median AQI 142004: Median AQI 112005: Median AQI 122009: Median AQI 382010: Median AQI 402011: Median AQI 392012: Median AQI 432013: Median AQI 412014: Median AQI 372015: Median AQI 362016: Median AQI 402017: Median AQI 412018: Median AQI 442019: Median AQI 392020: Median AQI 422021: Median AQI 442022: Median AQI 412023: Median AQI 462024: Median AQI 382025: Median AQI 38198020032005201020122014201620182020202220242025
  • 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)26974%
Ozone9626%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
20253652698565003862174PM2.5
20243662996610003856142PM2.5
2023365210137135004678164PM2.5
2022365268970000415881PM2.5
202136221214541004467154PM2.5
20203662561100000425993PM2.5
2019363268950000396090PM2.5
201836524412010004465129PM2.5
2017365276890000415786PM2.5
2016359268910000405784PM2.5
20153583035410003654125Ozone
2014354279750000375894Ozone
20133582551030000416184PM2.5
20123032109120004367115Ozone
20112241893500003956100Ozone
20104226160000407494PM2.5
2009393180000386576PM2.5
2005414100000122747PM10
2004565600000112230PM10
2003545400000142737PM10
2002494900000132833PM10
198032132100000122543NO2

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 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