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)

Franklin County had the highest share of days with good air quality (US EPA AQI) of 37 counties in 2017, at 98.9%. Mercer County had the lowest, at 24.4%. The median was 57.7%. Source: EPA.

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Highest98.9Franklin County
Lowest24.4Mercer County
Median57.737 counties

Map of counties, 2017

Adams County: 65.2 %Allegheny County: 30.4 %Armstrong County: 50.4 %Beaver County: 38.1 %Berks County: 50.4 %Blair County: 61.6 %Bradford County: 71.5 %Bucks County: 86.3 %Cambria County: 33.2 %Centre County: 47.7 %Chester County: 37.6 %Clearfield County: 91.6 %Cumberland County: 61.3 %Dauphin County: 55.9 %Delaware County: 43.3 %Elk County: 95.3 %Erie County: 63.3 %Franklin County: 98.9 %Greene County: 71.6 %Indiana County: 90.5 %Lackawanna County: 60.8 %Lancaster County: 33.4 %Lawrence County: 90.9 %Lebanon County: 31.2 %Lehigh County: 66 %Luzerne County: 97 %Lycoming County: 94.2 %Mercer County: 24.4 %Monroe County: 69.2 %Montgomery County: 57.7 %Northampton County: 28.8 %Philadelphia County: 26.3 %Somerset County: 94.2 %Tioga County: 41.3 %Washington County: 32.1 %Westmoreland County: 35.4 %York County: 54.2 %
  • Under 33
  • 33 to 43
  • 43 to 58
  • 58 to 66
  • 66 to 91
  • 91 and over
  • No data
%, 2017. 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, 2017

Franklin County: 98.9 %Franklin County98.9Luzerne County: 97 %Luzerne County97Elk County: 95.3 %Elk County95.3Lycoming County: 94.2 %Lycoming County94.2Somerset County: 94.2 %Somerset County94.2Clearfield County: 91.6 %Clearfield County91.6Lawrence County: 90.9 %Lawrence County90.9Indiana County: 90.5 %Indiana County90.5Bucks County: 86.3 %Bucks County86.3Greene County: 71.6 %Greene County71.6Bradford County: 71.5 %Bradford County71.5Monroe County: 69.2 %Monroe County69.2Lehigh County: 66 %Lehigh County66Adams County: 65.2 %Adams County65.2Erie County: 63.3 %Erie County63.3Blair County: 61.6 %Blair County61.6Cumberland County: 61.3 %Cumberland County61.3Lackawanna County: 60.8 %Lackawanna County60.8Montgomery County: 57.7 %Montgomery County57.7Dauphin County: 55.9 %Dauphin County55.9York County: 54.2 %York County54.2Armstrong County: 50.4 %Armstrong County50.4Berks County: 50.4 %Berks County50.4Centre County: 47.7 %Centre County47.7Delaware County: 43.3 %Delaware County43.3Tioga County: 41.3 %Tioga County41.3Beaver County: 38.1 %Beaver County38.1Chester County: 37.6 %Chester County37.6Westmoreland County: 35.4 %Westmoreland County35.4Lancaster County: 33.4 %Lancaster County33.4Cambria County: 33.2 %Cambria County33.2Washington County: 32.1 %Washington County32.1Lebanon County: 31.2 %Lebanon County31.2Allegheny County: 30.4 %Allegheny County30.4Northampton County: 28.8 %Northampton County28.8Philadelphia County: 26.3 %Philadelphia County26.3Mercer County: 24.4 %Mercer County24.4Franklin County: 98.9 %Franklin County98.9Luzerne County: 97 %Luzerne County97Elk County: 95.3 %Elk County95.3Lycoming County: 94.2 %Lycoming County94.2Somerset County: 94.2 %Somerset County94.2Clearfield County: 91.6 %Clearfield County91.6Lawrence County: 90.9 %Lawrence County90.9Indiana County: 90.5 %Indiana County90.5Bucks County: 86.3 %Bucks County86.3Greene County: 71.6 %Greene County71.6Bradford County: 71.5 %Bradford County71.5Monroe County: 69.2 %Monroe County69.2Lehigh County: 66 %Lehigh County66Adams County: 65.2 %Adams County65.2Erie County: 63.3 %Erie County63.3Blair County: 61.6 %Blair County61.6Cumberland County: 61.3 %Cumberland County61.3Lackawanna County: 60.8 %Lackawanna County60.8Montgomery County: 57.7 %Montgomery County57.7Dauphin County: 55.9 %Dauphin County55.9York County: 54.2 %York County54.2Armstrong County: 50.4 %Armstrong County50.4Berks County: 50.4 %Berks County50.4Centre County: 47.7 %Centre County47.7Delaware County: 43.3 %Delaware County43.3Tioga County: 41.3 %Tioga County41.3Beaver County: 38.1 %Beaver County38.1Chester County: 37.6 %Chester County37.6Westmoreland County: 35.4 %Westmoreland County35.4Lancaster County: 33.4 %Lancaster County33.4Cambria County: 33.2 %Cambria County33.2Washington County: 32.1 %Washington County32.1Lebanon County: 31.2 %Lebanon County31.2Allegheny County: 30.4 %Allegheny County30.4Northampton County: 28.8 %Northampton County28.8Philadelphia County: 26.3 %Philadelphia County26.3Mercer County: 24.4 %Mercer County24.4
%. Source: Invokely calculation with data from EPA. Retrieved 2026-10-12.

Full ranking

RankCounties2017 (%)Change on 2016
1Franklin County98.9+2.5 pts
2Luzerne County97+5.2 pts
3Elk County95.3+2.5 pts
4Lycoming County94.2+2.7 pts
4Somerset County94.2+3.4 pts
6Clearfield County91.6+1.4 pts
7Lawrence County90.9-0.9 pts
8Indiana County90.5+3.2 pts
9Bucks County86.3+0.3 pts
10Greene County71.6-12.1 pts
11Bradford County71.5+5 pts
12Monroe County69.2-3.2 pts
13Lehigh County66+23.4 pts
14Adams County65.2-0.1 pts
15Erie County63.3-0.4 pts
16Blair County61.6-1.2 pts
17Cumberland County61.3+13.4 pts
18Lackawanna County60.8-3.7 pts
19Montgomery County57.7-26.2 pts
20Dauphin County55.9+4.5 pts
21York County54.2+6.1 pts
22Armstrong County50.4+7.4 pts
22Berks County50.4+13.2 pts
24Centre County47.7-15.7 pts
25Delaware County43.3+10.2 pts
26Tioga County41.3-35.2 pts
27Beaver County38.1-8.3 pts
28Chester County37.6-5.7 pts
29Westmoreland County35.4-5 pts
30Lancaster County33.4+1.4 pts
31Cambria County33.2-24.5 pts
32Washington County32.1+4.5 pts
33Lebanon County31.2+5.2 pts
34Allegheny County30.4+2.3 pts
35Northampton County28.8-13 pts
36Philadelphia County26.3-4 pts
37Mercer County24.4-31.1 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. 7 counties with data in other periods have no value for 2017 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), 2017) [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), 2017. 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=2017. 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), 2017. 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=2017.

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), 2017 [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=2017 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_pennsylvania_by_2017,
  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), 2017}},
  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=2017. 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), 2017
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=2017
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/pennsylvania-counties?period=2017.
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)?

Franklin County, with 98.9% in 2017, according to EPA.

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

Mercer County, with 24.4% in 2017.

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. 7 counties have no value for 2017 and are not ranked.

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

Counties in Pennsylvania: more rankings