EnviroNearby

Porter County, Indiana air quality history

Daily Air Quality Index summaries from EPA monitors in Porter, Indiana, 1980–2025.

62%
Good days in 2025
44
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 Porter, Indiana on 365 days. 226 of those days (62%) were in the Good range, and the median daily AQI was 44. That median is higher than the typical monitored county in Indiana (median 41 across 33 counties), and higher than the typical monitored U.S. county (40). The main pollutant was ozone on 189 days. Across the years with fuller monitoring, the share of Good days fell: an average of 82% in 1980–1982 versus 62% 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 329 of 366 days1980: Moderate 22 of 366 days1980: Unhealthy for Sensitive Groups 11 of 366 days1980: Unhealthy 4 of 366 days19801981: Good 292 of 365 days1981: Moderate 44 of 365 days1981: Unhealthy for Sensitive Groups 22 of 365 days1981: Unhealthy 7 of 365 days1982: Good 259 of 334 days1982: Moderate 49 of 334 days1982: Unhealthy for Sensitive Groups 20 of 334 days1982: Unhealthy 5 of 334 days1982: Very Unhealthy 1 of 334 days1983: Good 265 of 365 days1983: Moderate 45 of 365 days1983: Unhealthy for Sensitive Groups 25 of 365 days1983: Unhealthy 25 of 365 days1983: Very Unhealthy 5 of 365 days1984: Good 265 of 366 days1984: Moderate 51 of 366 days1984: Unhealthy for Sensitive Groups 32 of 366 days1984: Unhealthy 13 of 366 days1984: Very Unhealthy 5 of 366 days1985: Good 219 of 313 days1985: Moderate 70 of 313 days1985: Unhealthy for Sensitive Groups 20 of 313 days1985: Unhealthy 2 of 313 days1985: Very Unhealthy 2 of 313 days19851986: Good 174 of 235 days1986: Moderate 42 of 235 days1986: Unhealthy for Sensitive Groups 15 of 235 days1986: Unhealthy 3 of 235 days1986: Very Unhealthy 1 of 235 days1987: Good 176 of 249 days1987: Moderate 46 of 249 days1987: Unhealthy for Sensitive Groups 18 of 249 days1987: Unhealthy 4 of 249 days1987: Very Unhealthy 5 of 249 days1988: Good 123 of 239 days1988: Moderate 50 of 239 days1988: Unhealthy for Sensitive Groups 36 of 239 days1988: Unhealthy 19 of 239 days1988: Very Unhealthy 11 of 239 days1989: Good 144 of 236 days1989: Moderate 56 of 236 days1989: Unhealthy for Sensitive Groups 29 of 236 days1989: Unhealthy 7 of 236 days1990: Good 115 of 239 days1990: Moderate 57 of 239 days1990: Unhealthy for Sensitive Groups 44 of 239 days1990: Unhealthy 21 of 239 days1990: Very Unhealthy 2 of 239 days19901991: Good 161 of 236 days1991: Moderate 47 of 236 days1991: Unhealthy for Sensitive Groups 20 of 236 days1991: Unhealthy 7 of 236 days1991: Very Unhealthy 1 of 236 days1992: Good 230 of 275 days1992: Moderate 29 of 275 days1992: Unhealthy for Sensitive Groups 11 of 275 days1992: Unhealthy 4 of 275 days1992: Very Unhealthy 1 of 275 days1993: Good 309 of 362 days1993: Moderate 44 of 362 days1993: Unhealthy for Sensitive Groups 8 of 362 days1993: Unhealthy 1 of 362 days1994: Good 302 of 365 days1994: Moderate 45 of 365 days1994: Unhealthy for Sensitive Groups 14 of 365 days1994: Unhealthy 3 of 365 days1994: Very Unhealthy 1 of 365 days1995: Good 262 of 349 days1995: Moderate 53 of 349 days1995: Unhealthy for Sensitive Groups 18 of 349 days1995: Unhealthy 13 of 349 days1995: Very Unhealthy 3 of 349 days19951996: Good 279 of 353 days1996: Moderate 49 of 353 days1996: Unhealthy for Sensitive Groups 17 of 353 days1996: Unhealthy 5 of 353 days1996: Very Unhealthy 2 of 353 days1996: Hazardous 1 of 353 days1997: Good 271 of 344 days1997: Moderate 54 of 344 days1997: Unhealthy for Sensitive Groups 10 of 344 days1997: Unhealthy 9 of 344 days1998: Good 245 of 353 days1998: Moderate 72 of 353 days1998: Unhealthy for Sensitive Groups 29 of 353 days1998: Unhealthy 6 of 353 days1998: Very Unhealthy 1 of 353 days1999: Good 229 of 365 days1999: Moderate 92 of 365 days1999: Unhealthy for Sensitive Groups 34 of 365 days1999: Unhealthy 10 of 365 days2000: Good 207 of 341 days2000: Moderate 121 of 341 days2000: Unhealthy for Sensitive Groups 9 of 341 days2000: Unhealthy 4 of 341 days20002001: Good 215 of 361 days2001: Moderate 118 of 361 days2001: Unhealthy for Sensitive Groups 26 of 361 days2001: Unhealthy 2 of 361 days2002: Good 221 of 365 days2002: Moderate 106 of 365 days2002: Unhealthy for Sensitive Groups 20 of 365 days2002: Unhealthy 17 of 365 days2002: Very Unhealthy 1 of 365 days2003: Good 229 of 363 days2003: Moderate 113 of 363 days2003: Unhealthy for Sensitive Groups 18 of 363 days2003: Unhealthy 3 of 363 days2004: Good 239 of 359 days2004: Moderate 111 of 359 days2004: Unhealthy for Sensitive Groups 8 of 359 days2004: Unhealthy 1 of 359 days2005: Good 208 of 364 days2005: Moderate 124 of 364 days2005: Unhealthy for Sensitive Groups 25 of 364 days2005: Unhealthy 6 of 364 days2005: Very Unhealthy 1 of 364 days20052006: Good 234 of 355 days2006: Moderate 116 of 355 days2006: Unhealthy for Sensitive Groups 5 of 355 days2007: Good 208 of 365 days2007: Moderate 137 of 365 days2007: Unhealthy for Sensitive Groups 16 of 365 days2007: Unhealthy 4 of 365 days2008: Good 132 of 366 days2008: Moderate 231 of 366 days2008: Unhealthy for Sensitive Groups 3 of 366 days2009: Good 105 of 365 days2009: Moderate 258 of 365 days2009: Unhealthy for Sensitive Groups 2 of 365 days2010: Good 107 of 365 days2010: Moderate 253 of 365 days2010: Unhealthy for Sensitive Groups 5 of 365 days20102011: Good 173 of 364 days2011: Moderate 186 of 364 days2011: Unhealthy for Sensitive Groups 4 of 364 days2011: Unhealthy 1 of 364 days2012: Good 128 of 366 days2012: Moderate 227 of 366 days2012: Unhealthy for Sensitive Groups 7 of 366 days2012: Unhealthy 3 of 366 days2012: Very Unhealthy 1 of 366 days2013: Good 172 of 365 days2013: Moderate 190 of 365 days2013: Unhealthy for Sensitive Groups 2 of 365 days2013: Unhealthy 1 of 365 days2014: Good 131 of 363 days2014: Moderate 227 of 363 days2014: Unhealthy for Sensitive Groups 5 of 363 days2015: Good 206 of 365 days2015: Moderate 155 of 365 days2015: Unhealthy for Sensitive Groups 3 of 365 days2015: Unhealthy 1 of 365 days20152016: Good 236 of 366 days2016: Moderate 123 of 366 days2016: Unhealthy for Sensitive Groups 7 of 366 days2017: Good 234 of 365 days2017: Moderate 122 of 365 days2017: Unhealthy for Sensitive Groups 9 of 365 days2018: Good 214 of 365 days2018: Moderate 146 of 365 days2018: Unhealthy for Sensitive Groups 4 of 365 days2018: Unhealthy 1 of 365 days2019: Good 236 of 365 days2019: Moderate 125 of 365 days2019: Unhealthy for Sensitive Groups 4 of 365 days2020: Good 247 of 366 days2020: Moderate 113 of 366 days2020: Unhealthy for Sensitive Groups 5 of 366 days2020: Unhealthy 1 of 366 days20202021: Good 204 of 365 days2021: Moderate 154 of 365 days2021: Unhealthy for Sensitive Groups 7 of 365 days2022: Good 229 of 365 days2022: Moderate 130 of 365 days2022: Unhealthy for Sensitive Groups 5 of 365 days2022: Very Unhealthy 1 of 365 days2023: Good 206 of 365 days2023: Moderate 137 of 365 days2023: Unhealthy for Sensitive Groups 20 of 365 days2023: Unhealthy 2 of 365 days2024: Good 243 of 366 days2024: Moderate 121 of 366 days2024: Unhealthy for Sensitive Groups 2 of 366 days2025: Good 226 of 365 days2025: Moderate 128 of 365 days2025: Unhealthy for Sensitive Groups 11 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 year0501001502001980: 90th percentile AQI 511981: 90th percentile AQI 901982: 90th percentile AQI 871983: 90th percentile AQI 1431984: 90th percentile AQI 1221985: 90th percentile AQI 971986: 90th percentile AQI 931987: 90th percentile AQI 1011988: 90th percentile AQI 1641989: 90th percentile AQI 1151990: 90th percentile AQI 1501991: 90th percentile AQI 1051992: 90th percentile AQI 671993: 90th percentile AQI 641994: 90th percentile AQI 671995: 90th percentile AQI 1001996: 90th percentile AQI 871997: 90th percentile AQI 801998: 90th percentile AQI 1011999: 90th percentile AQI 1052000: 90th percentile AQI 782001: 90th percentile AQI 902002: 90th percentile AQI 1052003: 90th percentile AQI 832004: 90th percentile AQI 772005: 90th percentile AQI 942006: 90th percentile AQI 692007: 90th percentile AQI 842008: 90th percentile AQI 752009: 90th percentile AQI 772010: 90th percentile AQI 802011: 90th percentile AQI 712012: 90th percentile AQI 842013: 90th percentile AQI 682014: 90th percentile AQI 762015: 90th percentile AQI 682016: 90th percentile AQI 672017: 90th percentile AQI 642018: 90th percentile AQI 642019: 90th percentile AQI 642020: 90th percentile AQI 612021: 90th percentile AQI 682022: 90th percentile AQI 622023: 90th percentile AQI 772024: 90th percentile AQI 642025: 90th percentile AQI 711980: Median AQI 251981: Median AQI 311982: Median AQI 331983: Median AQI 331984: Median AQI 391985: Median AQI 401986: Median AQI 411987: Median AQI 401988: Median AQI 501989: Median AQI 461990: Median AQI 511991: Median AQI 421992: Median AQI 331993: Median AQI 331994: Median AQI 331995: Median AQI 361996: Median AQI 311997: Median AQI 311998: Median AQI 321999: Median AQI 422000: Median AQI 432001: Median AQI 422002: Median AQI 432003: Median AQI 432004: Median AQI 402005: Median AQI 442006: Median AQI 412007: Median AQI 462008: Median AQI 552009: Median AQI 572010: Median AQI 572011: Median AQI 522012: Median AQI 562013: Median AQI 512014: Median AQI 552015: Median AQI 472016: Median AQI 442017: Median AQI 442018: Median AQI 472019: Median AQI 442020: Median AQI 432021: Median AQI 472022: Median AQI 462023: Median AQI 482024: Median AQI 442025: 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
Ozone18952%
Fine particles (PM2.5)16746%
Coarse particles (PM10)92%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
2025365226128110004471136Ozone
202436624312120004464112Ozone
2023365206137202004877180PM2.5
202236522913050104662202PM2.5
202136520415470004768136PM2.5
202036624711351004361151Ozone
201936523612540004464115PM2.5
201836521414641004764164PM2.5
201736523412290004464136PM2.5
201636623612370004467126PM2.5
201536520615531004768168PM2.5
201436313122750005576115PM2.5
201336517219021005168198PM2.5
201236612822773105684206PM2.5
201136417318641005271158PM2.5
201036510725350005780133PM2.5
200936510525820005777119PM2.5
200836613223130005575140PM2.5
2007365208137164004684164Ozone
200635523411650004169126Ozone
2005364208124256104494204Ozone
200435923911181004077174Ozone
2003363229113183004383161Ozone
200236522110620171043105215Ozone
2001361215118262004290174Ozone
200034120712194004378190Ozone
19993652299234100042105200Ozone
1998353245722961032101207PM10
199734427154109003180187PM10
199635327949175213187504PM10
19953492625318133036100204Ozone
199436530245143103367204Ozone
19933623094481003364156Ozone
199227523029114103367204Ozone
1991236161472071042105208Ozone
19902391155744212051150218Ozone
1989236144562970046115185Ozone
198823912350361911050164252Ozone
1987249176461845040101221Ozone
198623517442153104193203Ozone
198531321970202204097212Ozone
19843662655132135039122230Ozone
19833652654525255033143234Ozone
198233425949205103387214NO2
198136529244227003190185NO2
198036632922114002551190NO2

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 Indiana with a similar median AQI in 2025

All monitored counties in Indiana

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