EnviroNearby

Adams County, Illinois air quality history

Daily Air Quality Index summaries from EPA monitors in Adams, Illinois, 1980–2025.

95%
Good days in 2025
38
Median daily AQI, 2025
0
Days above 100 in 2025
244
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Adams, Illinois on 244 days. 231 of those days (95%) were in the Good range, and the median daily AQI was 38. That median is lower than the typical monitored county in Illinois (median 42 across 23 counties), and about the same as the typical monitored U.S. county (40). The main pollutant was ozone on 244 days. Across the years with fuller monitoring, the share of Good days held roughly steady: an average of 86% in 1980–1982 versus 87% in 2023–2025.

EPA did not report an AQI for every day of 2025 here (244 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 213 of 281 days1980: Moderate 49 of 281 days1980: Unhealthy for Sensitive Groups 18 of 281 days1980: Unhealthy 1 of 281 days19801981: Good 234 of 276 days1981: Moderate 38 of 276 days1981: Unhealthy for Sensitive Groups 4 of 276 days1982: Good 303 of 312 days1982: Moderate 9 of 312 days1983: Good 275 of 336 days1983: Moderate 48 of 336 days1983: Unhealthy for Sensitive Groups 13 of 336 days1984: Good 310 of 353 days1984: Moderate 37 of 353 days1984: Unhealthy for Sensitive Groups 6 of 353 days1985: Good 307 of 356 days1985: Moderate 31 of 356 days1985: Unhealthy for Sensitive Groups 18 of 356 days19851986: Good 284 of 312 days1986: Moderate 19 of 312 days1986: Unhealthy for Sensitive Groups 9 of 312 days1987: Good 298 of 342 days1987: Moderate 35 of 342 days1987: Unhealthy for Sensitive Groups 9 of 342 days1988: Good 281 of 353 days1988: Moderate 56 of 353 days1988: Unhealthy for Sensitive Groups 14 of 353 days1988: Unhealthy 2 of 353 days1989: Good 292 of 340 days1989: Moderate 43 of 340 days1989: Unhealthy for Sensitive Groups 5 of 340 days1990: Good 310 of 339 days1990: Moderate 28 of 339 days1990: Unhealthy for Sensitive Groups 1 of 339 days19901991: Good 309 of 356 days1991: Moderate 38 of 356 days1991: Unhealthy for Sensitive Groups 7 of 356 days1991: Unhealthy 2 of 356 days1992: Good 310 of 338 days1992: Moderate 19 of 338 days1992: Unhealthy for Sensitive Groups 7 of 338 days1992: Unhealthy 2 of 338 days1993: Good 351 of 364 days1993: Moderate 12 of 364 days1993: Unhealthy for Sensitive Groups 1 of 364 days1994: Good 331 of 354 days1994: Moderate 22 of 354 days1994: Unhealthy for Sensitive Groups 1 of 354 days1995: Good 325 of 358 days1995: Moderate 25 of 358 days1995: Unhealthy for Sensitive Groups 8 of 358 days19951996: Good 325 of 365 days1996: Moderate 33 of 365 days1996: Unhealthy for Sensitive Groups 4 of 365 days1996: Unhealthy 3 of 365 days1997: Good 326 of 358 days1997: Moderate 31 of 358 days1997: Unhealthy for Sensitive Groups 1 of 358 days1998: Good 311 of 360 days1998: Moderate 43 of 360 days1998: Unhealthy for Sensitive Groups 4 of 360 days1998: Unhealthy 2 of 360 days1999: Good 317 of 365 days1999: Moderate 40 of 365 days1999: Unhealthy for Sensitive Groups 7 of 365 days1999: Unhealthy 1 of 365 days2000: Good 308 of 364 days2000: Moderate 52 of 364 days2000: Unhealthy for Sensitive Groups 4 of 364 days20002001: Good 287 of 363 days2001: Moderate 68 of 363 days2001: Unhealthy for Sensitive Groups 6 of 363 days2001: Unhealthy 2 of 363 days2002: Good 280 of 364 days2002: Moderate 76 of 364 days2002: Unhealthy for Sensitive Groups 6 of 364 days2002: Unhealthy 2 of 364 days2003: Good 283 of 361 days2003: Moderate 74 of 361 days2003: Unhealthy for Sensitive Groups 4 of 361 days2004: Good 316 of 364 days2004: Moderate 48 of 364 days2005: Good 257 of 365 days2005: Moderate 93 of 365 days2005: Unhealthy for Sensitive Groups 15 of 365 days20052006: Good 284 of 362 days2006: Moderate 74 of 362 days2006: Unhealthy for Sensitive Groups 4 of 362 days2007: Good 255 of 334 days2007: Moderate 73 of 334 days2007: Unhealthy for Sensitive Groups 6 of 334 days2008: Good 321 of 357 days2008: Moderate 36 of 357 days2009: Good 323 of 363 days2009: Moderate 40 of 363 days2010: Good 300 of 353 days2010: Moderate 52 of 353 days2010: Unhealthy for Sensitive Groups 1 of 353 days20102011: Good 337 of 365 days2011: Moderate 28 of 365 days2012: Good 322 of 364 days2012: Moderate 37 of 364 days2012: Unhealthy for Sensitive Groups 4 of 364 days2012: Unhealthy 1 of 364 days2013: Good 282 of 303 days2013: Moderate 21 of 303 days2014: Good 192 of 213 days2014: Moderate 21 of 213 days2015: Good 193 of 214 days2015: Moderate 21 of 214 days20152016: Good 199 of 214 days2016: Moderate 15 of 214 days2017: Good 213 of 244 days2017: Moderate 30 of 244 days2017: Unhealthy for Sensitive Groups 1 of 244 days2018: Good 228 of 245 days2018: Moderate 17 of 245 days2019: Good 208 of 241 days2019: Moderate 33 of 241 days2020: Good 220 of 244 days2020: Moderate 24 of 244 days20202021: Good 219 of 242 days2021: Moderate 23 of 242 days2022: Good 230 of 237 days2022: Moderate 7 of 237 days2023: Good 184 of 245 days2023: Moderate 49 of 245 days2023: Unhealthy for Sensitive Groups 12 of 245 days2024: Good 210 of 233 days2024: Moderate 23 of 233 days2025: Good 231 of 244 days2025: Moderate 13 of 244 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 871981: 90th percentile AQI 611982: 90th percentile AQI 441983: 90th percentile AQI 711984: 90th percentile AQI 611985: 90th percentile AQI 711986: 90th percentile AQI 501987: 90th percentile AQI 541988: 90th percentile AQI 841989: 90th percentile AQI 611990: 90th percentile AQI 501991: 90th percentile AQI 581992: 90th percentile AQI 481993: 90th percentile AQI 441994: 90th percentile AQI 471995: 90th percentile AQI 481996: 90th percentile AQI 511997: 90th percentile AQI 491998: 90th percentile AQI 581999: 90th percentile AQI 582000: 90th percentile AQI 582001: 90th percentile AQI 622002: 90th percentile AQI 732003: 90th percentile AQI 652004: 90th percentile AQI 552005: 90th percentile AQI 872006: 90th percentile AQI 682007: 90th percentile AQI 692008: 90th percentile AQI 512009: 90th percentile AQI 512010: 90th percentile AQI 582011: 90th percentile AQI 492012: 90th percentile AQI 542013: 90th percentile AQI 482014: 90th percentile AQI 502015: 90th percentile AQI 502016: 90th percentile AQI 492017: 90th percentile AQI 542018: 90th percentile AQI 492019: 90th percentile AQI 542020: 90th percentile AQI 502021: 90th percentile AQI 502022: 90th percentile AQI 472023: 90th percentile AQI 772024: 90th percentile AQI 502025: 90th percentile AQI 491980: Median AQI 371981: Median AQI 361982: Median AQI 291983: Median AQI 321984: Median AQI 301985: Median AQI 331986: Median AQI 321987: Median AQI 311988: Median AQI 321989: Median AQI 341990: Median AQI 331991: Median AQI 341992: Median AQI 301993: Median AQI 291994: Median AQI 291995: Median AQI 311996: Median AQI 311997: Median AQI 341998: Median AQI 331999: Median AQI 322000: Median AQI 342001: Median AQI 362002: Median AQI 372003: Median AQI 362004: Median AQI 352005: Median AQI 402006: Median AQI 392007: Median AQI 382008: Median AQI 342009: Median AQI 342010: Median AQI 372011: Median AQI 372012: Median AQI 352013: Median AQI 372014: Median AQI 372015: Median AQI 402016: Median AQI 362017: Median AQI 412018: Median AQI 352019: Median AQI 412020: Median AQI 382021: Median AQI 402022: Median AQI 392023: Median AQI 432024: Median AQI 422025: Median AQI 381980198519901995200020052010201520202025
  • 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
Ozone244100%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
2025244231130000384971Ozone
2024233210230000425097Ozone
202324518449120004377136Ozone
202223723070000394771Ozone
2021242219230000405093Ozone
2020244220240000385084Ozone
2019241208330000415493Ozone
2018245228170000354987Ozone
20172442133010004154115Ozone
2016214199150000364980Ozone
2015214193210000405093Ozone
2014213192210000375090Ozone
2013303282210000374897Ozone
20123643223741003554151Ozone
20113653372800003749100Ozone
20103533005210003758122Ozone
2009363323400000345180Ozone
2008357321360000345193Ozone
20073342557360003869140Ozone
20063622847440003968119Ozone
200536525793150004087122Ozone
20043643164800003555100Ozone
20033612837440003665122Ozone
20023642807662003773154Ozone
20013632876862003662158Ozone
20003643085240003458129Ozone
19993653174071003258151Ozone
19983603114342003358159Ozone
19973583263110003449122Ozone
19963653253343003151172Ozone
19953583252580003148129Ozone
19943543312210002947101Ozone
19933643511210002944108Ozone
19923383101972003048156Ozone
19913563093872003458151Ozone
19903393102810003350122Ozone
19893402924350003461119Ozone
198835328156142003284161Ozone
19873422983590003154122Ozone
19863122841990003250133Ozone
198535630731180003371136Ozone
19843533103760003061133Ozone
198333627548130003271150Ozone
198231230390000294477Ozone
19812762343840003661136Ozone
198028121349181003787151Ozone

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 Illinois with a similar median AQI in 2025

All monitored counties in Illinois

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