EnviroNearby

Forest County, Wisconsin air quality history

Daily Air Quality Index summaries from EPA monitors in Forest, Wisconsin, 1994–2025.

75%
Good days in 2025
39
Median daily AQI, 2025
14
Days above 100 in 2025
361
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Forest, Wisconsin on 361 days. 271 of those days (75%) were in the Good range, and the median daily AQI was 39. 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 ozone on 209 days. Across the years with fuller monitoring, the share of Good days fell: an average of 90% in 2004–2006 versus 77% in 2023–2025.

Years with fewer than 120 monitored days (1994, 1995, 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%1994: Good 55 of 55 days19941995: Good 48 of 49 days1995: Moderate 1 of 49 days2002: Good 28 of 28 days20022003: Good 56 of 57 days2003: Moderate 1 of 57 days2004: Good 311 of 335 days2004: Moderate 23 of 335 days2004: Unhealthy for Sensitive Groups 1 of 335 days20042005: Good 294 of 350 days2005: Moderate 51 of 350 days2005: Unhealthy for Sensitive Groups 5 of 350 days2006: Good 329 of 358 days2006: Moderate 29 of 358 days20062007: Good 288 of 336 days2007: Moderate 43 of 336 days2007: Unhealthy for Sensitive Groups 5 of 336 days2008: Good 317 of 363 days2008: Moderate 45 of 363 days2008: Unhealthy for Sensitive Groups 1 of 363 days20082009: Good 335 of 358 days2009: Moderate 23 of 358 days2010: Good 328 of 362 days2010: Moderate 34 of 362 days20102011: Good 304 of 365 days2011: Moderate 60 of 365 days2011: Unhealthy for Sensitive Groups 1 of 365 days2012: Good 306 of 364 days2012: Moderate 53 of 364 days2012: Unhealthy for Sensitive Groups 5 of 364 days20122013: Good 300 of 362 days2013: Moderate 62 of 362 days2014: Good 314 of 364 days2014: Moderate 50 of 364 days20142015: Good 318 of 362 days2015: Moderate 43 of 362 days2015: Unhealthy for Sensitive Groups 1 of 362 days2016: Good 325 of 350 days2016: Moderate 24 of 350 days2016: Unhealthy for Sensitive Groups 1 of 350 days20162017: Good 327 of 364 days2017: Moderate 37 of 364 days2018: Good 300 of 365 days2018: Moderate 65 of 365 days20182019: Good 308 of 363 days2019: Moderate 55 of 363 days2020: Good 311 of 366 days2020: Moderate 55 of 366 days20202021: Good 282 of 361 days2021: Moderate 75 of 361 days2021: Unhealthy for Sensitive Groups 3 of 361 days2021: Unhealthy 1 of 361 days2022: Good 321 of 363 days2022: Moderate 42 of 363 days20222023: Good 252 of 363 days2023: Moderate 99 of 363 days2023: Unhealthy for Sensitive Groups 9 of 363 days2023: Unhealthy 3 of 363 days2024: Good 313 of 364 days2024: Moderate 50 of 364 days2024: Unhealthy 1 of 364 days20242025: Good 271 of 361 days2025: Moderate 76 of 361 days2025: Unhealthy for Sensitive Groups 7 of 361 days2025: Unhealthy 7 of 361 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 year0501001994: 90th percentile AQI 171995: 90th percentile AQI 242002: 90th percentile AQI 212003: 90th percentile AQI 232004: 90th percentile AQI 482005: 90th percentile AQI 642006: 90th percentile AQI 492007: 90th percentile AQI 572008: 90th percentile AQI 552009: 90th percentile AQI 472010: 90th percentile AQI 502011: 90th percentile AQI 552012: 90th percentile AQI 582013: 90th percentile AQI 552014: 90th percentile AQI 532015: 90th percentile AQI 522016: 90th percentile AQI 482017: 90th percentile AQI 512018: 90th percentile AQI 572019: 90th percentile AQI 532020: 90th percentile AQI 542021: 90th percentile AQI 592022: 90th percentile AQI 522023: 90th percentile AQI 692024: 90th percentile AQI 532025: 90th percentile AQI 641994: Median AQI 71995: Median AQI 62002: Median AQI 102003: Median AQI 82004: Median AQI 362005: Median AQI 372006: Median AQI 352007: Median AQI 342008: Median AQI 372009: Median AQI 332010: Median AQI 362011: Median AQI 372012: Median AQI 362013: Median AQI 382014: Median AQI 362015: Median AQI 352016: Median AQI 342017: Median AQI 362018: Median AQI 382019: Median AQI 362020: Median AQI 362021: Median AQI 382022: Median AQI 372023: Median AQI 422024: Median AQI 372025: Median AQI 3919942002200420062008201020122014201620182020202220242025
  • 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
Ozone20958%
Fine particles (PM2.5)15242%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
20253612717677003964182Ozone
20243643135001003753153Ozone
20233632529993004269178Ozone
2022363321420000375277Ozone
20213612827531003859165Ozone
2020366311550000365493Ozone
2019363308550000365397Ozone
2018365300650000385793Ozone
2017364327370000365174Ozone
20163503252410003448101Ozone
20153623184310003552102Ozone
2014364314500000365387Ozone
2013362300620000385584Ozone
20123643065350003658140Ozone
20113653046010003755115Ozone
2010362328340000365093Ozone
2009358335230000334790Ozone
20083633174510003755105Ozone
20073362884350003457133Ozone
2006358329290000354997Ozone
20053502945150003764140Ozone
20043353112310003648108Ozone
200357561000082353PM10
2002282800000102127PM10
199549481000062452PM10
199455550000071731PM10

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 1994–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem