EnviroNearby

Lehigh County, Pennsylvania air quality history

Daily Air Quality Index summaries from EPA monitors in Lehigh, Pennsylvania, 1980–2025.

72%
Good days in 2025
41
Median daily AQI, 2025
1
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 Lehigh, Pennsylvania on 361 days. 260 of those days (72%) were in the Good range, and the median daily AQI was 41. That median is about the same as the typical monitored county in Pennsylvania (median 40 across 38 counties), and about the same as the typical monitored U.S. county (40). The main pollutant was ozone on 225 days. Across the years with fuller monitoring, the share of Good days held roughly steady: an average of 69% in 1980–1982 versus 70% 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 221 of 340 days1980: Moderate 65 of 340 days1980: Unhealthy for Sensitive Groups 29 of 340 days1980: Unhealthy 20 of 340 days1980: Very Unhealthy 4 of 340 days1980: Hazardous 1 of 340 days19801981: Good 244 of 345 days1981: Moderate 66 of 345 days1981: Unhealthy for Sensitive Groups 22 of 345 days1981: Unhealthy 11 of 345 days1981: Very Unhealthy 2 of 345 days1982: Good 257 of 361 days1982: Moderate 67 of 361 days1982: Unhealthy for Sensitive Groups 24 of 361 days1982: Unhealthy 12 of 361 days1982: Very Unhealthy 1 of 361 days1983: Good 228 of 365 days1983: Moderate 106 of 365 days1983: Unhealthy for Sensitive Groups 22 of 365 days1983: Unhealthy 9 of 365 days1984: Good 228 of 366 days1984: Moderate 101 of 366 days1984: Unhealthy for Sensitive Groups 24 of 366 days1984: Unhealthy 12 of 366 days1984: Very Unhealthy 1 of 366 days1985: Good 257 of 365 days1985: Moderate 80 of 365 days1985: Unhealthy for Sensitive Groups 23 of 365 days1985: Unhealthy 5 of 365 days19851986: Good 254 of 365 days1986: Moderate 76 of 365 days1986: Unhealthy for Sensitive Groups 25 of 365 days1986: Unhealthy 10 of 365 days1987: Good 246 of 365 days1987: Moderate 73 of 365 days1987: Unhealthy for Sensitive Groups 27 of 365 days1987: Unhealthy 15 of 365 days1987: Very Unhealthy 4 of 365 days1988: Good 258 of 366 days1988: Moderate 64 of 366 days1988: Unhealthy for Sensitive Groups 25 of 366 days1988: Unhealthy 14 of 366 days1988: Very Unhealthy 5 of 366 days1989: Good 268 of 365 days1989: Moderate 70 of 365 days1989: Unhealthy for Sensitive Groups 21 of 365 days1989: Unhealthy 6 of 365 days1990: Good 294 of 365 days1990: Moderate 41 of 365 days1990: Unhealthy for Sensitive Groups 21 of 365 days1990: Unhealthy 9 of 365 days19901991: Good 267 of 365 days1991: Moderate 59 of 365 days1991: Unhealthy for Sensitive Groups 31 of 365 days1991: Unhealthy 6 of 365 days1991: Very Unhealthy 2 of 365 days1992: Good 316 of 366 days1992: Moderate 37 of 366 days1992: Unhealthy for Sensitive Groups 12 of 366 days1992: Unhealthy 1 of 366 days1993: Good 276 of 365 days1993: Moderate 60 of 365 days1993: Unhealthy for Sensitive Groups 26 of 365 days1993: Unhealthy 3 of 365 days1994: Good 258 of 365 days1994: Moderate 84 of 365 days1994: Unhealthy for Sensitive Groups 21 of 365 days1994: Unhealthy 2 of 365 days1995: Good 282 of 365 days1995: Moderate 59 of 365 days1995: Unhealthy for Sensitive Groups 18 of 365 days1995: Unhealthy 6 of 365 days19951996: Good 286 of 366 days1996: Moderate 47 of 366 days1996: Unhealthy for Sensitive Groups 27 of 366 days1996: Unhealthy 6 of 366 days1997: Good 287 of 365 days1997: Moderate 44 of 365 days1997: Unhealthy for Sensitive Groups 22 of 365 days1997: Unhealthy 11 of 365 days1997: Very Unhealthy 1 of 365 days1998: Good 269 of 365 days1998: Moderate 49 of 365 days1998: Unhealthy for Sensitive Groups 33 of 365 days1998: Unhealthy 14 of 365 days1999: Good 193 of 365 days1999: Moderate 129 of 365 days1999: Unhealthy for Sensitive Groups 26 of 365 days1999: Unhealthy 15 of 365 days1999: Very Unhealthy 2 of 365 days2000: Good 139 of 366 days2000: Moderate 197 of 366 days2000: Unhealthy for Sensitive Groups 24 of 366 days2000: Unhealthy 5 of 366 days2000: Very Unhealthy 1 of 366 days20002001: Good 135 of 365 days2001: Moderate 187 of 365 days2001: Unhealthy for Sensitive Groups 34 of 365 days2001: Unhealthy 8 of 365 days2001: Very Unhealthy 1 of 365 days2002: Good 137 of 365 days2002: Moderate 185 of 365 days2002: Unhealthy for Sensitive Groups 26 of 365 days2002: Unhealthy 15 of 365 days2002: Very Unhealthy 2 of 365 days2003: Good 141 of 365 days2003: Moderate 199 of 365 days2003: Unhealthy for Sensitive Groups 21 of 365 days2003: Unhealthy 3 of 365 days2003: Very Unhealthy 1 of 365 days2004: Good 118 of 366 days2004: Moderate 227 of 366 days2004: Unhealthy for Sensitive Groups 18 of 366 days2004: Unhealthy 3 of 366 days2005: Good 121 of 365 days2005: Moderate 215 of 365 days2005: Unhealthy for Sensitive Groups 25 of 365 days2005: Unhealthy 4 of 365 days20052006: Good 312 of 364 days2006: Moderate 41 of 364 days2006: Unhealthy for Sensitive Groups 8 of 364 days2006: Unhealthy 3 of 364 days2007: Good 301 of 365 days2007: Moderate 41 of 365 days2007: Unhealthy for Sensitive Groups 21 of 365 days2007: Unhealthy 2 of 365 days2008: Good 302 of 366 days2008: Moderate 49 of 366 days2008: Unhealthy for Sensitive Groups 14 of 366 days2008: Unhealthy 1 of 366 days2009: Good 336 of 362 days2009: Moderate 24 of 362 days2009: Unhealthy for Sensitive Groups 2 of 362 days2010: Good 278 of 363 days2010: Moderate 65 of 363 days2010: Unhealthy for Sensitive Groups 18 of 363 days2010: Unhealthy 2 of 363 days20102011: Good 302 of 351 days2011: Moderate 40 of 351 days2011: Unhealthy for Sensitive Groups 9 of 351 days2012: Good 308 of 362 days2012: Moderate 44 of 362 days2012: Unhealthy for Sensitive Groups 9 of 362 days2012: Unhealthy 1 of 362 days2013: Good 317 of 365 days2013: Moderate 46 of 365 days2013: Unhealthy for Sensitive Groups 2 of 365 days2014: Good 334 of 365 days2014: Moderate 30 of 365 days2014: Unhealthy for Sensitive Groups 1 of 365 days2015: Good 319 of 365 days2015: Moderate 43 of 365 days2015: Unhealthy for Sensitive Groups 3 of 365 days20152016: Good 156 of 366 days2016: Moderate 204 of 366 days2016: Unhealthy for Sensitive Groups 6 of 366 days2017: Good 241 of 365 days2017: Moderate 123 of 365 days2017: Unhealthy for Sensitive Groups 1 of 365 days2018: Good 221 of 365 days2018: Moderate 142 of 365 days2018: Unhealthy for Sensitive Groups 2 of 365 days2019: Good 254 of 360 days2019: Moderate 103 of 360 days2019: Unhealthy for Sensitive Groups 3 of 360 days2020: Good 262 of 359 days2020: Moderate 97 of 359 days20202021: Good 198 of 353 days2021: Moderate 154 of 353 days2021: Unhealthy 1 of 353 days2022: Good 246 of 359 days2022: Moderate 113 of 359 days2023: Good 230 of 363 days2023: Moderate 126 of 363 days2023: Unhealthy for Sensitive Groups 2 of 363 days2023: Unhealthy 4 of 363 days2023: Hazardous 1 of 363 days2024: Good 267 of 353 days2024: Moderate 84 of 353 days2024: Unhealthy for Sensitive Groups 2 of 353 days2025: Good 260 of 361 days2025: Moderate 100 of 361 days2025: Unhealthy for Sensitive Groups 1 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 year0501001501980: 90th percentile AQI 1331981: 90th percentile AQI 1011982: 90th percentile AQI 1011983: 90th percentile AQI 931984: 90th percentile AQI 1011985: 90th percentile AQI 931986: 90th percentile AQI 971987: 90th percentile AQI 1121988: 90th percentile AQI 1121989: 90th percentile AQI 801990: 90th percentile AQI 841991: 90th percentile AQI 1011992: 90th percentile AQI 581993: 90th percentile AQI 901994: 90th percentile AQI 871995: 90th percentile AQI 871996: 90th percentile AQI 901997: 90th percentile AQI 971998: 90th percentile AQI 1221999: 90th percentile AQI 1082000: 90th percentile AQI 922001: 90th percentile AQI 1092002: 90th percentile AQI 1122003: 90th percentile AQI 912004: 90th percentile AQI 882005: 90th percentile AQI 962006: 90th percentile AQI 642007: 90th percentile AQI 802008: 90th percentile AQI 772009: 90th percentile AQI 472010: 90th percentile AQI 872011: 90th percentile AQI 642012: 90th percentile AQI 642013: 90th percentile AQI 542014: 90th percentile AQI 492015: 90th percentile AQI 582016: 90th percentile AQI 682017: 90th percentile AQI 622018: 90th percentile AQI 712019: 90th percentile AQI 642020: 90th percentile AQI 582021: 90th percentile AQI 662022: 90th percentile AQI 612023: 90th percentile AQI 672024: 90th percentile AQI 612025: 90th percentile AQI 631980: Median AQI 431981: Median AQI 421982: Median AQI 411983: Median AQI 431984: Median AQI 461985: Median AQI 411986: Median AQI 421987: Median AQI 421988: Median AQI 421989: Median AQI 411990: Median AQI 381991: Median AQI 401992: Median AQI 371993: Median AQI 401994: Median AQI 421995: Median AQI 381996: Median AQI 381997: Median AQI 381998: Median AQI 391999: Median AQI 482000: Median AQI 562001: Median AQI 572002: Median AQI 552003: Median AQI 552004: Median AQI 572005: Median AQI 582006: Median AQI 322007: Median AQI 342008: Median AQI 322009: Median AQI 252010: Median AQI 312011: Median AQI 322012: Median AQI 342013: Median AQI 352014: Median AQI 352015: Median AQI 342016: Median AQI 522017: Median AQI 442018: Median AQI 432019: Median AQI 432020: Median AQI 412021: Median AQI 472022: Median AQI 422023: Median AQI 432024: Median AQI 392025: Median AQI 411980198519901995200020052010201520202025
  • 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
Ozone22562%
Fine particles (PM2.5)13537%
Coarse particles (PM10)1<1%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
202536126010010004163115Ozone
20243532678420003961119Ozone
202336323012624014367337PM2.5
20223592461130000426199PM2.5
202135319815401004766154PM2.5
2020359262970000415893PM2.5
201936025410330004364119PM2.5
201836522114220004371126PM2.5
201736524112310004462115Ozone
201636615620460005268129PM2.5
20153653194330003458108Ozone
20143653343010003549112Ozone
20133653174620003554101Ozone
20123623084491003464151Ozone
20113513024090003264147Ozone
201036327865182003187172Ozone
20093623362420002547108Ozone
200836630249141003277164Ozone
200736530141212003480164Ozone
20063643124183003264166Ozone
2005365121215254005896166PM2.5
2004366118227183005788174PM2.5
2003365141199213105591202PM2.5
200236513718526152055112203PM2.5
20013651351873481057109204PM2.5
2000366139197245105692207PM2.5
199936519312926152048108213Ozone
19983652694933140039122182Ozone
1997365287442211103897207Ozone
199636628647276003890197NO2
199536528259186003887195NO2
199436525884212004287190NO2
199336527660263004090174NO2
199236631637121003758159Ozone
1991365267593162040101202Ozone
199036529441219003884197Ozone
198936526870216004180166NO2
19883662586425145042112225NO2
19873652467327154042112218Ozone
1986365254762510004297187NO2
198536525780235004193174Ozone
198436622810124121046101201Ozone
1983365228106229004393197CO
19823612576724121041101205Ozone
19813452446622112042101206NO2
19803402216529204143133357NO2

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 Pennsylvania with a similar median AQI in 2025

All monitored counties in Pennsylvania

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