Data / Rankings / Share of days with good air quality (US EPA AQI) / Counties in Pennsylvania

Counties in Pennsylvania by share of days with good air quality (US EPA AQI)

Lawrence County had the highest share of days with good air quality (US EPA AQI) of 38 counties in 2024, at 100%. Philadelphia County had the lowest, at 47.3%. The median was 75.4%. Source: EPA.

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Highest100Lawrence County
Lowest47.3Philadelphia County
Median75.438 counties

Map of counties, 2024

Adams County: 63.1 %Allegheny County: 47.8 %Armstrong County: 75.3 %Beaver County: 57.9 %Berks County: 69.4 %Blair County: 80.9 %Bradford County: 82.1 %Bucks County: 82.3 %Cambria County: 73.7 %Centre County: 78.4 %Chester County: 72.7 %Cumberland County: 72.6 %Dauphin County: 56.3 %Delaware County: 68.3 %Elk County: 95.8 %Erie County: 80.6 %Fayette County: 73.5 %Franklin County: 93.3 %Greene County: 85.2 %Indiana County: 81.5 %Lackawanna County: 72.4 %Lancaster County: 51.6 %Lawrence County: 100 %Lebanon County: 66.1 %Lehigh County: 75.6 %Lycoming County: 76.8 %Mercer County: 74.9 %Monroe County: 91.4 %Montgomery County: 72.9 %Northampton County: 76 %Philadelphia County: 47.3 %Somerset County: 90.2 %Susquehanna County: 89.7 %Tioga County: 87.3 %Washington County: 61.2 %Westmoreland County: 76.6 %Wyoming County: 90.6 %York County: 65.6 %
  • Under 64
  • 64 to 73
  • 73 to 75
  • 75 to 81
  • 81 to 89
  • 89 and over
  • No data
%, 2024. Hatched areas have no value for this period. Source: Invokely calculation with data from EPA. Boundaries: U.S. Census Bureau cartographic boundary files.

All counties, 2024

Lawrence County: 100 %Lawrence County100Elk County: 95.8 %Elk County95.8Franklin County: 93.3 %Franklin County93.3Monroe County: 91.4 %Monroe County91.4Wyoming County: 90.6 %Wyoming County90.6Somerset County: 90.2 %Somerset County90.2Susquehanna County: 89.7 %Susquehanna County89.7Tioga County: 87.3 %Tioga County87.3Greene County: 85.2 %Greene County85.2Bucks County: 82.3 %Bucks County82.3Bradford County: 82.1 %Bradford County82.1Indiana County: 81.5 %Indiana County81.5Blair County: 80.9 %Blair County80.9Erie County: 80.6 %Erie County80.6Centre County: 78.4 %Centre County78.4Lycoming County: 76.8 %Lycoming County76.8Westmoreland County: 76.6 %Westmoreland County76.6Northampton County: 76 %Northampton County76Lehigh County: 75.6 %Lehigh County75.6Armstrong County: 75.3 %Armstrong County75.3Mercer County: 74.9 %Mercer County74.9Cambria County: 73.7 %Cambria County73.7Fayette County: 73.5 %Fayette County73.5Montgomery County: 72.9 %Montgomery County72.9Chester County: 72.7 %Chester County72.7Cumberland County: 72.6 %Cumberland County72.6Lackawanna County: 72.4 %Lackawanna County72.4Berks County: 69.4 %Berks County69.4Delaware County: 68.3 %Delaware County68.3Lebanon County: 66.1 %Lebanon County66.1York County: 65.6 %York County65.6Adams County: 63.1 %Adams County63.1Washington County: 61.2 %Washington County61.2Beaver County: 57.9 %Beaver County57.9Dauphin County: 56.3 %Dauphin County56.3Lancaster County: 51.6 %Lancaster County51.6Allegheny County: 47.8 %Allegheny County47.8Philadelphia County: 47.3 %Philadelphia County47.3Lawrence County: 100 %Lawrence County100Elk County: 95.8 %Elk County95.8Franklin County: 93.3 %Franklin County93.3Monroe County: 91.4 %Monroe County91.4Wyoming County: 90.6 %Wyoming County90.6Somerset County: 90.2 %Somerset County90.2Susquehanna County: 89.7 %Susquehanna County89.7Tioga County: 87.3 %Tioga County87.3Greene County: 85.2 %Greene County85.2Bucks County: 82.3 %Bucks County82.3Bradford County: 82.1 %Bradford County82.1Indiana County: 81.5 %Indiana County81.5Blair County: 80.9 %Blair County80.9Erie County: 80.6 %Erie County80.6Centre County: 78.4 %Centre County78.4Lycoming County: 76.8 %Lycoming County76.8Westmoreland County: 76.6 %Westmoreland County76.6Northampton County: 76 %Northampton County76Lehigh County: 75.6 %Lehigh County75.6Armstrong County: 75.3 %Armstrong County75.3Mercer County: 74.9 %Mercer County74.9Cambria County: 73.7 %Cambria County73.7Fayette County: 73.5 %Fayette County73.5Montgomery County: 72.9 %Montgomery County72.9Chester County: 72.7 %Chester County72.7Cumberland County: 72.6 %Cumberland County72.6Lackawanna County: 72.4 %Lackawanna County72.4Berks County: 69.4 %Berks County69.4Delaware County: 68.3 %Delaware County68.3Lebanon County: 66.1 %Lebanon County66.1York County: 65.6 %York County65.6Adams County: 63.1 %Adams County63.1Washington County: 61.2 %Washington County61.2Beaver County: 57.9 %Beaver County57.9Dauphin County: 56.3 %Dauphin County56.3Lancaster County: 51.6 %Lancaster County51.6Allegheny County: 47.8 %Allegheny County47.8Philadelphia County: 47.3 %Philadelphia County47.3
%. Source: Invokely calculation with data from EPA. Retrieved 2026-10-12.

Full ranking

RankCounties2024 (%)Change on 2023
1Lawrence County100+4.9 pts
2Elk County95.8+1.3 pts
3Franklin County93.3+4.6 pts
4Monroe County91.4-0.4 pts
5Wyoming County90.6+6.4 pts
6Somerset County90.2-1 pts
7Susquehanna County89.7+6.8 pts
8Tioga County87.3+3.7 pts
9Greene County85.2+12.7 pts
10Bucks County82.3+0.9 pts
11Bradford County82.1+0.1 pts
12Indiana County81.5+8.8 pts
13Blair County80.9+16.9 pts
14Erie County80.6+14.8 pts
15Centre County78.4+12.9 pts
16Lycoming County76.8-8.7 pts
17Westmoreland County76.6+0.4 pts
18Northampton County76+18.3 pts
19Lehigh County75.6+12.2 pts
20Armstrong County75.3+9.6 pts
21Mercer County74.9+9.8 pts
22Cambria County73.7+15 pts
23Fayette County73.5+1.1 pts
24Montgomery County72.9+9.3 pts
25Chester County72.7+11.8 pts
26Cumberland County72.6+14.5 pts
27Lackawanna County72.4+9.4 pts
28Berks County69.4+13.1 pts
29Delaware County68.3+17.1 pts
30Lebanon County66.1+10.2 pts
31York County65.6+10 pts
32Adams County63.1+11.6 pts
33Washington County61.2+11.9 pts
34Beaver County57.9+14.6 pts
35Dauphin County56.3+10 pts
36Lancaster County51.6+22 pts
37Allegheny County47.8+14.6 pts
38Philadelphia County47.3+24.6 pts

Other periods

About this ranking

Days with a daily Air Quality Index of 0 to 50 (good) as a percentage of the days of the year with an AQI in a US county. Calculated by Invokely from the day counts in the EPA AirData annual summaries; both counts are stored with each value.

United States counties with air quality monitors only, about 1,000 of some 3,100 in recent years; a county without monitors has no value. The number of days with an AQI differs between counties because some monitors run only in the ozone season.

Every value in the ranking comes from the same publisher and the same period, so the counties are compared on one definition. 6 counties with data in other periods have no value for 2024 and are left out rather than filled from another source. Equal values share a rank.

How to cite

U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Retrieved 2026-10-12.

Citation styles

The publisher is the author. Invokely is named only as the place the figures were read, where a style asks for it.

APA 7

U.S. Environmental Protection Agency. (2026). EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts (Counties in Pennsylvania by share of days with good air quality (US EPA AQI), 2024) [Data set]. Retrieved October 12, 2026, from https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual

MLA 9

EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts, Counties in Pennsylvania by share of days with good air quality (US EPA AQI), 2024. U.S. Environmental Protection Agency, 13 July 2026, https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Invokely, https://invokely.ai/rankings/good-air-quality-days-share/pennsylvania-counties?period=2024. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Environmental Protection Agency. 2026. EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts. Counties in Pennsylvania by share of days with good air quality (US EPA AQI), 2024. Dataset. Accessed October 12, 2026. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Also distributed by Invokely, https://invokely.ai/rankings/good-air-quality-days-share/pennsylvania-counties?period=2024.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts, Counties in Pennsylvania by share of days with good air quality (US EPA AQI), 2024 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/rankings/good-air-quality-days-share/pennsylvania-counties?period=2024 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_pennsylvania_by_2024,
  author = {{U.S. Environmental Protection Agency}},
  title = {{EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts: Counties in Pennsylvania by share of days with good air quality (US EPA AQI), 2024}},
  year = {2026},
  howpublished = {Data set},
  url = {https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual},
  urldate = {2026-10-12},
  note = {Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/pennsylvania-counties?period=2024. Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts. https://aqs.epa.gov/aqsweb/airdata/download\_files.html\#Annual. Retrieved 2026-10-12.},
}
RIS
TY  - DATA
AU  - U.S. Environmental Protection Agency
TI  - EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts: Counties in Pennsylvania by share of days with good air quality (US EPA AQI), 2024
PY  - 2026
DA  - 2026/07/13
PB  - U.S. Environmental Protection Agency
DB  - Invokely
UR  - https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual
L2  - https://invokely.ai/rankings/good-air-quality-days-share/pennsylvania-counties?period=2024
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/pennsylvania-counties?period=2024.
N1  - Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Retrieved 2026-10-12.
ER  -
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Questions

Which county has the highest share of days with good air quality (US EPA AQI)?

Lawrence County, with 100% in 2024, according to EPA.

Which county has the lowest share of days with good air quality (US EPA AQI)?

Philadelphia County, with 47.3% in 2024.

Where does this ranking come from?

Every value comes from one source and one period, so the places are comparable: U.S. Environmental Protection Agency, EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts. Retrieved 2026-10-12. 6 counties have no value for 2024 and are not ranked.

Share of days with good air quality (US EPA AQI): other rankings

Counties in Pennsylvania: more rankings