EnviroNearby

Madison County, Illinois air quality history

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

52%
Good days in 2025
49
Median daily AQI, 2025
4
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 Madison, Illinois on 365 days. 191 of those days (52%) were in the Good range, and the median daily AQI was 49. That median is higher than the typical monitored county in Illinois (median 42 across 23 counties), and higher than the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 240 days. Across the years with fuller monitoring, the share of Good days fell: an average of 63% in 1980–1982 versus 45% in 2023–2025.

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 214 of 365 days1980: Moderate 89 of 365 days1980: Unhealthy for Sensitive Groups 34 of 365 days1980: Unhealthy 17 of 365 days1980: Very Unhealthy 11 of 365 days19801981: Good 257 of 364 days1981: Moderate 77 of 364 days1981: Unhealthy for Sensitive Groups 23 of 364 days1981: Unhealthy 7 of 364 days1982: Good 219 of 362 days1982: Moderate 115 of 362 days1982: Unhealthy for Sensitive Groups 22 of 362 days1982: Unhealthy 6 of 362 days1983: Good 217 of 365 days1983: Moderate 86 of 365 days1983: Unhealthy for Sensitive Groups 31 of 365 days1983: Unhealthy 20 of 365 days1983: Very Unhealthy 11 of 365 days1984: Good 224 of 366 days1984: Moderate 91 of 366 days1984: Unhealthy for Sensitive Groups 33 of 366 days1984: Unhealthy 15 of 366 days1984: Very Unhealthy 3 of 366 days1985: Good 230 of 365 days1985: Moderate 95 of 365 days1985: Unhealthy for Sensitive Groups 29 of 365 days1985: Unhealthy 8 of 365 days1985: Very Unhealthy 3 of 365 days19851986: Good 181 of 365 days1986: Moderate 140 of 365 days1986: Unhealthy for Sensitive Groups 27 of 365 days1986: Unhealthy 13 of 365 days1986: Very Unhealthy 4 of 365 days1987: Good 171 of 365 days1987: Moderate 146 of 365 days1987: Unhealthy for Sensitive Groups 40 of 365 days1987: Unhealthy 7 of 365 days1987: Very Unhealthy 1 of 365 days1988: Good 174 of 366 days1988: Moderate 129 of 366 days1988: Unhealthy for Sensitive Groups 39 of 366 days1988: Unhealthy 17 of 366 days1988: Very Unhealthy 7 of 366 days1989: Good 158 of 365 days1989: Moderate 173 of 365 days1989: Unhealthy for Sensitive Groups 29 of 365 days1989: Unhealthy 4 of 365 days1989: Very Unhealthy 1 of 365 days1990: Good 236 of 365 days1990: Moderate 82 of 365 days1990: Unhealthy for Sensitive Groups 34 of 365 days1990: Unhealthy 11 of 365 days1990: Very Unhealthy 2 of 365 days19901991: Good 247 of 365 days1991: Moderate 72 of 365 days1991: Unhealthy for Sensitive Groups 36 of 365 days1991: Unhealthy 9 of 365 days1991: Very Unhealthy 1 of 365 days1992: Good 253 of 366 days1992: Moderate 83 of 366 days1992: Unhealthy for Sensitive Groups 26 of 366 days1992: Unhealthy 4 of 366 days1993: Good 256 of 365 days1993: Moderate 85 of 365 days1993: Unhealthy for Sensitive Groups 20 of 365 days1993: Unhealthy 3 of 365 days1993: Very Unhealthy 1 of 365 days1994: Good 207 of 365 days1994: Moderate 108 of 365 days1994: Unhealthy for Sensitive Groups 37 of 365 days1994: Unhealthy 13 of 365 days1995: Good 202 of 365 days1995: Moderate 117 of 365 days1995: Unhealthy for Sensitive Groups 23 of 365 days1995: Unhealthy 22 of 365 days1995: Very Unhealthy 1 of 365 days19951996: Good 226 of 366 days1996: Moderate 105 of 366 days1996: Unhealthy for Sensitive Groups 23 of 366 days1996: Unhealthy 11 of 366 days1996: Very Unhealthy 1 of 366 days1997: Good 229 of 365 days1997: Moderate 104 of 365 days1997: Unhealthy for Sensitive Groups 24 of 365 days1997: Unhealthy 7 of 365 days1997: Very Unhealthy 1 of 365 days1998: Good 206 of 365 days1998: Moderate 118 of 365 days1998: Unhealthy for Sensitive Groups 30 of 365 days1998: Unhealthy 11 of 365 days1999: Good 183 of 365 days1999: Moderate 131 of 365 days1999: Unhealthy for Sensitive Groups 40 of 365 days1999: Unhealthy 10 of 365 days1999: Very Unhealthy 1 of 365 days2000: Good 145 of 366 days2000: Moderate 190 of 366 days2000: Unhealthy for Sensitive Groups 27 of 366 days2000: Unhealthy 3 of 366 days2000: Very Unhealthy 1 of 366 days20002001: Good 134 of 365 days2001: Moderate 189 of 365 days2001: Unhealthy for Sensitive Groups 37 of 365 days2001: Unhealthy 5 of 365 days2002: Good 128 of 365 days2002: Moderate 184 of 365 days2002: Unhealthy for Sensitive Groups 33 of 365 days2002: Unhealthy 19 of 365 days2002: Very Unhealthy 1 of 365 days2003: Good 153 of 365 days2003: Moderate 177 of 365 days2003: Unhealthy for Sensitive Groups 29 of 365 days2003: Unhealthy 6 of 365 days2004: Good 168 of 366 days2004: Moderate 178 of 366 days2004: Unhealthy for Sensitive Groups 18 of 366 days2004: Unhealthy 2 of 366 days2005: Good 145 of 365 days2005: Moderate 173 of 365 days2005: Unhealthy for Sensitive Groups 36 of 365 days2005: Unhealthy 11 of 365 days20052006: Good 163 of 365 days2006: Moderate 174 of 365 days2006: Unhealthy for Sensitive Groups 26 of 365 days2006: Unhealthy 2 of 365 days2007: Good 175 of 365 days2007: Moderate 155 of 365 days2007: Unhealthy for Sensitive Groups 28 of 365 days2007: Unhealthy 6 of 365 days2007: Very Unhealthy 1 of 365 days2008: Good 171 of 366 days2008: Moderate 188 of 366 days2008: Unhealthy for Sensitive Groups 7 of 366 days2009: Good 84 of 365 days2009: Moderate 274 of 365 days2009: Unhealthy for Sensitive Groups 7 of 365 days2010: Good 41 of 365 days2010: Moderate 298 of 365 days2010: Unhealthy for Sensitive Groups 24 of 365 days2010: Unhealthy 2 of 365 days20102011: Good 139 of 364 days2011: Moderate 199 of 364 days2011: Unhealthy for Sensitive Groups 22 of 364 days2011: Unhealthy 4 of 364 days2012: Good 91 of 366 days2012: Moderate 238 of 366 days2012: Unhealthy for Sensitive Groups 30 of 366 days2012: Unhealthy 7 of 366 days2013: Good 149 of 365 days2013: Moderate 206 of 365 days2013: Unhealthy for Sensitive Groups 10 of 365 days2014: Good 165 of 365 days2014: Moderate 191 of 365 days2014: Unhealthy for Sensitive Groups 9 of 365 days2015: Good 194 of 365 days2015: Moderate 165 of 365 days2015: Unhealthy for Sensitive Groups 6 of 365 days20152016: Good 176 of 366 days2016: Moderate 181 of 366 days2016: Unhealthy for Sensitive Groups 9 of 366 days2017: Good 155 of 365 days2017: Moderate 201 of 365 days2017: Unhealthy for Sensitive Groups 9 of 365 days2018: Good 159 of 365 days2018: Moderate 196 of 365 days2018: Unhealthy for Sensitive Groups 8 of 365 days2018: Unhealthy 2 of 365 days2019: Good 140 of 363 days2019: Moderate 220 of 363 days2019: Unhealthy for Sensitive Groups 1 of 363 days2019: Unhealthy 2 of 363 days2020: Good 129 of 365 days2020: Moderate 233 of 365 days2020: Unhealthy for Sensitive Groups 3 of 365 days20202021: Good 82 of 365 days2021: Moderate 277 of 365 days2021: Unhealthy for Sensitive Groups 6 of 365 days2022: Good 134 of 363 days2022: Moderate 220 of 363 days2022: Unhealthy for Sensitive Groups 9 of 363 days2023: Good 113 of 363 days2023: Moderate 234 of 363 days2023: Unhealthy for Sensitive Groups 14 of 363 days2023: Unhealthy 2 of 363 days2024: Good 193 of 366 days2024: Moderate 167 of 366 days2024: Unhealthy for Sensitive Groups 4 of 366 days2024: Unhealthy 2 of 366 days2025: Good 191 of 365 days2025: Moderate 170 of 365 days2025: Unhealthy for Sensitive Groups 3 of 365 days2025: Very Unhealthy 1 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 year0501001501980: 90th percentile AQI 1361981: 90th percentile AQI 931982: 90th percentile AQI 901983: 90th percentile AQI 1361984: 90th percentile AQI 1191985: 90th percentile AQI 1011986: 90th percentile AQI 1121987: 90th percentile AQI 1121988: 90th percentile AQI 1291989: 90th percentile AQI 1001990: 90th percentile AQI 1051991: 90th percentile AQI 1121992: 90th percentile AQI 901993: 90th percentile AQI 841994: 90th percentile AQI 1121995: 90th percentile AQI 1151996: 90th percentile AQI 1001997: 90th percentile AQI 971998: 90th percentile AQI 1051999: 90th percentile AQI 1152000: 90th percentile AQI 972001: 90th percentile AQI 1012002: 90th percentile AQI 1222003: 90th percentile AQI 1002004: 90th percentile AQI 872005: 90th percentile AQI 1082006: 90th percentile AQI 952007: 90th percentile AQI 1002008: 90th percentile AQI 812009: 90th percentile AQI 752010: 90th percentile AQI 922011: 90th percentile AQI 902012: 90th percentile AQI 1012013: 90th percentile AQI 772014: 90th percentile AQI 772015: 90th percentile AQI 712016: 90th percentile AQI 712017: 90th percentile AQI 772018: 90th percentile AQI 742019: 90th percentile AQI 732020: 90th percentile AQI 712021: 90th percentile AQI 742022: 90th percentile AQI 712023: 90th percentile AQI 812024: 90th percentile AQI 712025: 90th percentile AQI 701980: Median AQI 461981: Median AQI 431982: Median AQI 451983: Median AQI 451984: Median AQI 451985: Median AQI 421986: Median AQI 511987: Median AQI 521988: Median AQI 521989: Median AQI 541990: Median AQI 431991: Median AQI 411992: Median AQI 411993: Median AQI 401994: Median AQI 461995: Median AQI 461996: Median AQI 441997: Median AQI 441998: Median AQI 461999: Median AQI 502000: Median AQI 562001: Median AQI 602002: Median AQI 592003: Median AQI 552004: Median AQI 532005: Median AQI 582006: Median AQI 522007: Median AQI 522008: Median AQI 522009: Median AQI 582010: Median AQI 642011: Median AQI 562012: Median AQI 582013: Median AQI 562014: Median AQI 532015: Median AQI 482016: Median AQI 512017: Median AQI 532018: Median AQI 532019: Median AQI 552020: Median AQI 542021: Median AQI 572022: Median AQI 542023: Median AQI 552024: Median AQI 492025: Median AQI 491980198519901995200020052010201520202025
  • 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)24066%
Ozone12233%
Coarse particles (PM10)31%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
202536519117030104970260PM2.5
202436619316742004971165PM2.5
2023363113234142005581155PM2.5
202236313422090005471147PM2.5
20213658227760005774143PM2.5
202036512923330005471112PM2.5
201936314022012005573156PM2.5
201836515919682005374154PM2.5
201736515520190005377136PM2.5
201636617618190005171129PM2.5
201536519416560004871115Ozone
201436516519190005377137Ozone
2013365149206100005677136PM2.5
2012366912383070058101200PM2.5
2011364139199224005690156PM2.5
201036541298242006492151PM2.5
20093658427470005875147PM2.5
200836617118870005281140Ozone
20073651751552861052100202Ozone
2006365163174262005295174Ozone
200536514517336110058108197Ozone
2004366168178182005387177Ozone
20033651531772960055100197Ozone
200236512818433191059122215Ozone
20013651341893750060101161Ozone
2000366145190273105697202Ozone
199936518313140101050115206Ozone
199836520611830110046105197Ozone
1997365229104247104497202Ozone
199636622610523111044100202Ozone
199536520211723221046115202Ozone
199436520710837130046112192Ozone
199336525685203104084205Ozone
199236625383264004190177Ozone
1991365247723691041112207Ozone
19903652368234112043105207Ozone
19893651581732941054100206PM10
198836617412939177052129219Ozone
19873651711464071052112203Ozone
198636518114027134051112215Ozone
1985365230952983042101214Ozone
19843662249133153045119221Ozone
198336521786312011045136242Ozone
1982362219115226004590185Ozone
198136425777237004393177Ozone
198036521489341711046136233Ozone

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