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)

Bradford County had the highest share of days with good air quality (US EPA AQI) of 37 counties in 2015, at 96.4%. Washington County had the lowest, at 27.4%. The median was 47.7%. Source: EPA.

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Highest96.4Bradford County
Lowest27.4Washington County
Median47.737 counties

Map of counties, 2015

Adams County: 48.2 %Allegheny County: 28.8 %Armstrong County: 38.7 %Beaver County: 47.7 %Berks County: 40.5 %Blair County: 46 %Bradford County: 96.4 %Bucks County: 42.8 %Cambria County: 35.6 %Centre County: 55.9 %Chester County: 36.4 %Clearfield County: 86.9 %Cumberland County: 36.6 %Dauphin County: 32.9 %Delaware County: 32.9 %Elk County: 93.4 %Erie County: 60.5 %Franklin County: 94.7 %Greene County: 83.1 %Indiana County: 82.6 %Lackawanna County: 48.2 %Lancaster County: 33.2 %Lawrence County: 91 %Lebanon County: 47.7 %Lehigh County: 87.4 %Luzerne County: 90.1 %Lycoming County: 93.7 %Mercer County: 43.6 %Monroe County: 66.8 %Montgomery County: 56.4 %Northampton County: 34 %Philadelphia County: 28.2 %Somerset County: 94.8 %Tioga County: 61.4 %Washington County: 27.4 %Westmoreland County: 46 %York County: 37 %
  • Under 34
  • 34 to 41
  • 41 to 48
  • 48 to 61
  • 61 to 90
  • 90 and over
  • No data
%, 2015. 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, 2015

Bradford County: 96.4 %Bradford County96.4Somerset County: 94.8 %Somerset County94.8Franklin County: 94.7 %Franklin County94.7Lycoming County: 93.7 %Lycoming County93.7Elk County: 93.4 %Elk County93.4Lawrence County: 91 %Lawrence County91Luzerne County: 90.1 %Luzerne County90.1Lehigh County: 87.4 %Lehigh County87.4Clearfield County: 86.9 %Clearfield County86.9Greene County: 83.1 %Greene County83.1Indiana County: 82.6 %Indiana County82.6Monroe County: 66.8 %Monroe County66.8Tioga County: 61.4 %Tioga County61.4Erie County: 60.5 %Erie County60.5Montgomery County: 56.4 %Montgomery County56.4Centre County: 55.9 %Centre County55.9Adams County: 48.2 %Adams County48.2Lackawanna County: 48.2 %Lackawanna County48.2Beaver County: 47.7 %Beaver County47.7Lebanon County: 47.7 %Lebanon County47.7Blair County: 46 %Blair County46Westmoreland County: 46 %Westmoreland County46Mercer County: 43.6 %Mercer County43.6Bucks County: 42.8 %Bucks County42.8Berks County: 40.5 %Berks County40.5Armstrong County: 38.7 %Armstrong County38.7York County: 37 %York County37Cumberland County: 36.6 %Cumberland County36.6Chester County: 36.4 %Chester County36.4Cambria County: 35.6 %Cambria County35.6Northampton County: 34 %Northampton County34Lancaster County: 33.2 %Lancaster County33.2Dauphin County: 32.9 %Dauphin County32.9Delaware County: 32.9 %Delaware County32.9Allegheny County: 28.8 %Allegheny County28.8Philadelphia County: 28.2 %Philadelphia County28.2Washington County: 27.4 %Washington County27.4Bradford County: 96.4 %Bradford County96.4Somerset County: 94.8 %Somerset County94.8Franklin County: 94.7 %Franklin County94.7Lycoming County: 93.7 %Lycoming County93.7Elk County: 93.4 %Elk County93.4Lawrence County: 91 %Lawrence County91Luzerne County: 90.1 %Luzerne County90.1Lehigh County: 87.4 %Lehigh County87.4Clearfield County: 86.9 %Clearfield County86.9Greene County: 83.1 %Greene County83.1Indiana County: 82.6 %Indiana County82.6Monroe County: 66.8 %Monroe County66.8Tioga County: 61.4 %Tioga County61.4Erie County: 60.5 %Erie County60.5Montgomery County: 56.4 %Montgomery County56.4Centre County: 55.9 %Centre County55.9Adams County: 48.2 %Adams County48.2Lackawanna County: 48.2 %Lackawanna County48.2Beaver County: 47.7 %Beaver County47.7Lebanon County: 47.7 %Lebanon County47.7Blair County: 46 %Blair County46Westmoreland County: 46 %Westmoreland County46Mercer County: 43.6 %Mercer County43.6Bucks County: 42.8 %Bucks County42.8Berks County: 40.5 %Berks County40.5Armstrong County: 38.7 %Armstrong County38.7York County: 37 %York County37Cumberland County: 36.6 %Cumberland County36.6Chester County: 36.4 %Chester County36.4Cambria County: 35.6 %Cambria County35.6Northampton County: 34 %Northampton County34Lancaster County: 33.2 %Lancaster County33.2Dauphin County: 32.9 %Dauphin County32.9Delaware County: 32.9 %Delaware County32.9Allegheny County: 28.8 %Allegheny County28.8Philadelphia County: 28.2 %Philadelphia County28.2Washington County: 27.4 %Washington County27.4
%. Source: Invokely calculation with data from EPA. Retrieved 2026-10-12.

Full ranking

RankCounties2015 (%)Change on 2014
1Bradford County96.4-3.6 pts
2Somerset County94.8-0.8 pts
3Franklin County94.7+2.4 pts
4Lycoming County93.7-0.5 pts
5Elk County93.4-0.8 pts
6Lawrence County91-1.3 pts
7Luzerne County90.1-4.4 pts
8Lehigh County87.4-4.1 pts
9Clearfield County86.9-8.2 pts
10Greene County83.1-7.2 pts
11Indiana County82.6-9.2 pts
12Monroe County66.8+8.6 pts
13Tioga County61.4-28.7 pts
14Erie County60.5+17.9 pts
15Montgomery County56.4-1.1 pts
16Centre County55.9+7.4 pts
17Adams County48.2-12.6 pts
17Lackawanna County48.2-2.5 pts
19Beaver County47.7+6.6 pts
19Lebanon County47.7+12.6 pts
21Blair County46+4.6 pts
21Westmoreland County46+1.9 pts
23Mercer County43.6+12.4 pts
24Bucks County42.8+2.8 pts
25Berks County40.5-2 pts
26Armstrong County38.7+1.1 pts
27York County37-5.5 pts
28Cumberland County36.6-2.1 pts
29Chester County36.4-6 pts
30Cambria County35.6-5.8 pts
31Northampton County34-6.5 pts
32Lancaster County33.2+17.3 pts
33Dauphin County32.9-7.9 pts
33Delaware County32.9+6.6 pts
35Allegheny County28.8+1.7 pts
36Philadelphia County28.2+14.5 pts
37Washington County27.4+5.8 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 2015 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), 2015) [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), 2015. 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=2015. 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), 2015. 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=2015.

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), 2015 [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=2015 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_pennsylvania_by_2015,
  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), 2015}},
  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=2015. 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), 2015
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=2015
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/pennsylvania-counties?period=2015.
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)?

Bradford County, with 96.4% in 2015, according to EPA.

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

Washington County, with 27.4% in 2015.

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 2015 and are not ranked.

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

Counties in Pennsylvania: more rankings