EnviroNearby

Warren County, Ohio air quality history

Daily Air Quality Index summaries from EPA monitors in Warren, Ohio, 1980–2025.

68%
Good days in 2025
44
Median daily AQI, 2025
7
Days above 100 in 2025
364
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Warren, Ohio on 364 days. 247 of those days (68%) were in the Good range, and the median daily AQI was 44. That median is about the same as the typical monitored county in Ohio (median 43 across 36 counties), and higher than the typical monitored U.S. county (40). The main pollutant was ozone on 200 days. Across the years with fuller monitoring, the share of Good days fell: an average of 77% in 1980–1982 versus 68% 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 263 of 337 days1980: Moderate 35 of 337 days1980: Unhealthy for Sensitive Groups 22 of 337 days1980: Unhealthy 12 of 337 days1980: Very Unhealthy 5 of 337 days19801981: Good 281 of 361 days1981: Moderate 43 of 361 days1981: Unhealthy for Sensitive Groups 24 of 361 days1981: Unhealthy 12 of 361 days1981: Very Unhealthy 1 of 361 days1982: Good 267 of 361 days1982: Moderate 53 of 361 days1982: Unhealthy for Sensitive Groups 23 of 361 days1982: Unhealthy 18 of 361 days1983: Good 232 of 350 days1983: Moderate 58 of 350 days1983: Unhealthy for Sensitive Groups 34 of 350 days1983: Unhealthy 20 of 350 days1983: Very Unhealthy 6 of 350 days1984: Good 251 of 328 days1984: Moderate 43 of 328 days1984: Unhealthy for Sensitive Groups 26 of 328 days1984: Unhealthy 8 of 328 days1985: Good 228 of 326 days1985: Moderate 58 of 326 days1985: Unhealthy for Sensitive Groups 31 of 326 days1985: Unhealthy 9 of 326 days19851986: Good 112 of 180 days1986: Moderate 33 of 180 days1986: Unhealthy for Sensitive Groups 24 of 180 days1986: Unhealthy 9 of 180 days1986: Very Unhealthy 2 of 180 days1987: Good 111 of 208 days1987: Moderate 59 of 208 days1987: Unhealthy for Sensitive Groups 22 of 208 days1987: Unhealthy 15 of 208 days1987: Very Unhealthy 1 of 208 days1988: Good 108 of 210 days1988: Moderate 48 of 210 days1988: Unhealthy for Sensitive Groups 22 of 210 days1988: Unhealthy 23 of 210 days1988: Very Unhealthy 9 of 210 days1989: Good 112 of 212 days1989: Moderate 61 of 212 days1989: Unhealthy for Sensitive Groups 26 of 212 days1989: Unhealthy 12 of 212 days1989: Very Unhealthy 1 of 212 days1990: Good 123 of 213 days1990: Moderate 46 of 213 days1990: Unhealthy for Sensitive Groups 28 of 213 days1990: Unhealthy 13 of 213 days1990: Very Unhealthy 3 of 213 days19901991: Good 99 of 211 days1991: Moderate 57 of 211 days1991: Unhealthy for Sensitive Groups 38 of 211 days1991: Unhealthy 14 of 211 days1991: Very Unhealthy 3 of 211 days1992: Good 144 of 214 days1992: Moderate 54 of 214 days1992: Unhealthy for Sensitive Groups 14 of 214 days1992: Unhealthy 2 of 214 days1993: Good 114 of 209 days1993: Moderate 60 of 209 days1993: Unhealthy for Sensitive Groups 26 of 209 days1993: Unhealthy 9 of 209 days1994: Good 113 of 209 days1994: Moderate 60 of 209 days1994: Unhealthy for Sensitive Groups 20 of 209 days1994: Unhealthy 15 of 209 days1994: Very Unhealthy 1 of 209 days1995: Good 108 of 208 days1995: Moderate 54 of 208 days1995: Unhealthy for Sensitive Groups 32 of 208 days1995: Unhealthy 11 of 208 days1995: Very Unhealthy 3 of 208 days19951996: Good 128 of 214 days1996: Moderate 49 of 214 days1996: Unhealthy for Sensitive Groups 28 of 214 days1996: Unhealthy 8 of 214 days1996: Very Unhealthy 1 of 214 days1997: Good 133 of 212 days1997: Moderate 51 of 212 days1997: Unhealthy for Sensitive Groups 20 of 212 days1997: Unhealthy 7 of 212 days1997: Very Unhealthy 1 of 212 days1998: Good 100 of 213 days1998: Moderate 65 of 213 days1998: Unhealthy for Sensitive Groups 32 of 213 days1998: Unhealthy 15 of 213 days1998: Very Unhealthy 1 of 213 days1999: Good 100 of 214 days1999: Moderate 66 of 214 days1999: Unhealthy for Sensitive Groups 38 of 214 days1999: Unhealthy 10 of 214 days2000: Good 142 of 213 days2000: Moderate 57 of 213 days2000: Unhealthy for Sensitive Groups 10 of 213 days2000: Unhealthy 4 of 213 days20002001: Good 137 of 214 days2001: Moderate 54 of 214 days2001: Unhealthy for Sensitive Groups 20 of 214 days2001: Unhealthy 3 of 214 days2002: Good 119 of 214 days2002: Moderate 51 of 214 days2002: Unhealthy for Sensitive Groups 30 of 214 days2002: Unhealthy 13 of 214 days2002: Very Unhealthy 1 of 214 days2003: Good 131 of 212 days2003: Moderate 55 of 212 days2003: Unhealthy for Sensitive Groups 16 of 212 days2003: Unhealthy 9 of 212 days2003: Very Unhealthy 1 of 212 days2004: Good 137 of 213 days2004: Moderate 55 of 213 days2004: Unhealthy for Sensitive Groups 20 of 213 days2004: Unhealthy 1 of 213 days2005: Good 111 of 212 days2005: Moderate 64 of 212 days2005: Unhealthy for Sensitive Groups 33 of 212 days2005: Unhealthy 4 of 212 days20052006: Good 117 of 214 days2006: Moderate 72 of 214 days2006: Unhealthy for Sensitive Groups 21 of 214 days2006: Unhealthy 4 of 214 days2007: Good 90 of 258 days2007: Moderate 116 of 258 days2007: Unhealthy for Sensitive Groups 48 of 258 days2007: Unhealthy 4 of 258 days2008: Good 113 of 258 days2008: Moderate 127 of 258 days2008: Unhealthy for Sensitive Groups 16 of 258 days2008: Unhealthy 2 of 258 days2009: Good 141 of 264 days2009: Moderate 115 of 264 days2009: Unhealthy for Sensitive Groups 8 of 264 days2010: Good 84 of 365 days2010: Moderate 270 of 365 days2010: Unhealthy for Sensitive Groups 11 of 365 days20102011: Good 95 of 350 days2011: Moderate 237 of 350 days2011: Unhealthy for Sensitive Groups 17 of 350 days2011: Unhealthy 1 of 350 days2012: Good 70 of 361 days2012: Moderate 280 of 361 days2012: Unhealthy for Sensitive Groups 9 of 361 days2012: Unhealthy 2 of 361 days2013: Good 30 of 349 days2013: Moderate 316 of 349 days2013: Unhealthy for Sensitive Groups 3 of 349 days2014: Good 82 of 342 days2014: Moderate 255 of 342 days2014: Unhealthy for Sensitive Groups 5 of 342 days2015: Good 200 of 344 days2015: Moderate 140 of 344 days2015: Unhealthy for Sensitive Groups 4 of 344 days20152016: Good 186 of 360 days2016: Moderate 165 of 360 days2016: Unhealthy for Sensitive Groups 9 of 360 days2017: Good 185 of 358 days2017: Moderate 172 of 358 days2017: Unhealthy for Sensitive Groups 1 of 358 days2018: Good 201 of 358 days2018: Moderate 152 of 358 days2018: Unhealthy for Sensitive Groups 5 of 358 days2019: Good 210 of 360 days2019: Moderate 147 of 360 days2019: Unhealthy for Sensitive Groups 3 of 360 days2020: Good 248 of 361 days2020: Moderate 109 of 361 days2020: Unhealthy for Sensitive Groups 4 of 361 days20202021: Good 230 of 360 days2021: Moderate 128 of 360 days2021: Unhealthy for Sensitive Groups 2 of 360 days2022: Good 231 of 356 days2022: Moderate 122 of 356 days2022: Unhealthy for Sensitive Groups 3 of 356 days2023: Good 230 of 364 days2023: Moderate 127 of 364 days2023: Unhealthy for Sensitive Groups 5 of 364 days2023: Unhealthy 2 of 364 days2024: Good 267 of 365 days2024: Moderate 92 of 365 days2024: Unhealthy for Sensitive Groups 6 of 365 days2025: Good 247 of 364 days2025: Moderate 110 of 364 days2025: Unhealthy for Sensitive Groups 7 of 364 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 year0501001502001980: 90th percentile AQI 1081981: 90th percentile AQI 1011982: 90th percentile AQI 1081983: 90th percentile AQI 1361984: 90th percentile AQI 1011985: 90th percentile AQI 1081986: 90th percentile AQI 1361987: 90th percentile AQI 1401988: 90th percentile AQI 1771989: 90th percentile AQI 1331990: 90th percentile AQI 1331991: 90th percentile AQI 1401992: 90th percentile AQI 931993: 90th percentile AQI 1191994: 90th percentile AQI 1331995: 90th percentile AQI 1401996: 90th percentile AQI 1191997: 90th percentile AQI 1081998: 90th percentile AQI 1401999: 90th percentile AQI 1332000: 90th percentile AQI 872001: 90th percentile AQI 1012002: 90th percentile AQI 1292003: 90th percentile AQI 1122004: 90th percentile AQI 1002005: 90th percentile AQI 1222006: 90th percentile AQI 1052007: 90th percentile AQI 1222008: 90th percentile AQI 932009: 90th percentile AQI 742010: 90th percentile AQI 842011: 90th percentile AQI 872012: 90th percentile AQI 772013: 90th percentile AQI 742014: 90th percentile AQI 772015: 90th percentile AQI 682016: 90th percentile AQI 742017: 90th percentile AQI 642018: 90th percentile AQI 672019: 90th percentile AQI 642020: 90th percentile AQI 612021: 90th percentile AQI 652022: 90th percentile AQI 632023: 90th percentile AQI 722024: 90th percentile AQI 642025: 90th percentile AQI 671980: Median AQI 201981: Median AQI 321982: Median AQI 351983: Median AQI 411984: Median AQI 341985: Median AQI 391986: Median AQI 431987: Median AQI 481988: Median AQI 501989: Median AQI 501990: Median AQI 471991: Median AQI 581992: Median AQI 441993: Median AQI 491994: Median AQI 471995: Median AQI 491996: Median AQI 461997: Median AQI 451998: Median AQI 541999: Median AQI 542000: Median AQI 452001: Median AQI 452002: Median AQI 482003: Median AQI 462004: Median AQI 462005: Median AQI 502006: Median AQI 482007: Median AQI 572008: Median AQI 522009: Median AQI 502010: Median AQI 592011: Median AQI 572012: Median AQI 582013: Median AQI 602014: Median AQI 572015: Median AQI 472016: Median AQI 502017: Median AQI 492018: Median AQI 482019: Median AQI 472020: Median AQI 442021: Median AQI 442022: Median AQI 442023: Median AQI 442024: Median AQI 432025: Median AQI 441980198519901995200020052010201520202025
  • 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
Ozone20055%
Fine particles (PM2.5)16445%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
202536424711070004467126Ozone
20243652679260004364147Ozone
202336423012752004472183PM2.5
202235623112230004463133PM2.5
202136023012820004465119PM2.5
202036124810940004461115PM2.5
201936021014730004764122PM2.5
201835820115250004867136PM2.5
201735818517210004964115PM2.5
201636018616590005074129PM2.5
201534420014040004768129PM2.5
20143428225550005777112PM2.5
20133493031630006074112PM2.5
20123617028092005877166PM2.5
201135095237171005787166PM2.5
201036584270110005984150PM2.5
200926414111580005074133Ozone
2008258113127162005293166Ozone
2007258901164840057122195Ozone
2006214117722140048105166Ozone
2005212111643340050122190Ozone
2004213137552010046100154Ozone
2003212131551691046112213Ozone
20022141195130131048129206Ozone
2001214137542030045101169Ozone
200021314257104004587200Ozone
19992141006638100054133195Ozone
19982131006532151054140212Ozone
1997212133512071045108206Ozone
1996214128492881046119204Ozone
19952081085432113049140215Ozone
19942091136020151047133201Ozone
1993209114602690049119172Ozone
199221414454142004493166Ozone
1991211995738143058140220Ozone
19902131234628133047133215Ozone
19892121126126121050133202Ozone
19882101084822239050177227Ozone
19872081115922151048140210Ozone
1986180112332492043136229Ozone
1985326228583190039108197Ozone
1984328251432680034101187Ozone
19833502325834206041136212Ozone
19823612675323180035108195Ozone
19813612814324121032101210Ozone
19803372633522125020108216Ozone

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 Ohio with a similar median AQI in 2025

All monitored counties in Ohio

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