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)

Clearfield County had the highest share of days with good air quality (US EPA AQI) of 40 counties in 2021, at 98.9%. Lancaster County had the lowest, at 27.4%. The median was 62.2%. Source: EPA.

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Highest98.9Clearfield County
Lowest27.4Lancaster County
Median62.240 counties

Map of counties, 2021

Adams County: 56.6 %Allegheny County: 32.3 %Armstrong County: 52.6 %Beaver County: 46.6 %Berks County: 54.2 %Blair County: 61.3 %Bradford County: 68 %Bucks County: 84.5 %Cambria County: 47.9 %Centre County: 66 %Chester County: 62 %Clearfield County: 98.9 %Cumberland County: 57.3 %Dauphin County: 43.2 %Delaware County: 49.9 %Elk County: 95 %Erie County: 77.5 %Fayette County: 64.1 %Franklin County: 95.1 %Greene County: 68.2 %Indiana County: 62.6 %Lackawanna County: 71.4 %Lancaster County: 27.4 %Lawrence County: 93.2 %Lebanon County: 54 %Lehigh County: 56.1 %Luzerne County: 94.1 %Lycoming County: 62.4 %Mercer County: 76.3 %Monroe County: 91.8 %Montgomery County: 56.7 %Northampton County: 58.6 %Philadelphia County: 37.5 %Somerset County: 93.4 %Susquehanna County: 75.4 %Tioga County: 78.3 %Washington County: 51.2 %Westmoreland County: 55.4 %Wyoming County: 75.6 %York County: 47.1 %
  • Under 49
  • 49 to 56
  • 56 to 62
  • 62 to 71
  • 71 to 88
  • 88 and over
  • No data
%, 2021. 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, 2021

Clearfield County: 98.9 %Clearfield County98.9Franklin County: 95.1 %Franklin County95.1Elk County: 95 %Elk County95Luzerne County: 94.1 %Luzerne County94.1Somerset County: 93.4 %Somerset County93.4Lawrence County: 93.2 %Lawrence County93.2Monroe County: 91.8 %Monroe County91.8Bucks County: 84.5 %Bucks County84.5Tioga County: 78.3 %Tioga County78.3Erie County: 77.5 %Erie County77.5Mercer County: 76.3 %Mercer County76.3Wyoming County: 75.6 %Wyoming County75.6Susquehanna County: 75.4 %Susquehanna County75.4Lackawanna County: 71.4 %Lackawanna County71.4Greene County: 68.2 %Greene County68.2Bradford County: 68 %Bradford County68Centre County: 66 %Centre County66Fayette County: 64.1 %Fayette County64.1Indiana County: 62.6 %Indiana County62.6Lycoming County: 62.4 %Lycoming County62.4Chester County: 62 %Chester County62Blair County: 61.3 %Blair County61.3Northampton County: 58.6 %Northampton County58.6Cumberland County: 57.3 %Cumberland County57.3Montgomery County: 56.7 %Montgomery County56.7Adams County: 56.6 %Adams County56.6Lehigh County: 56.1 %Lehigh County56.1Westmoreland County: 55.4 %Westmoreland County55.4Berks County: 54.2 %Berks County54.2Lebanon County: 54 %Lebanon County54Armstrong County: 52.6 %Armstrong County52.6Washington County: 51.2 %Washington County51.2Delaware County: 49.9 %Delaware County49.9Cambria County: 47.9 %Cambria County47.9York County: 47.1 %York County47.1Beaver County: 46.6 %Beaver County46.6Dauphin County: 43.2 %Dauphin County43.2Philadelphia County: 37.5 %Philadelphia County37.5Allegheny County: 32.3 %Allegheny County32.3Lancaster County: 27.4 %Lancaster County27.4Clearfield County: 98.9 %Clearfield County98.9Franklin County: 95.1 %Franklin County95.1Elk County: 95 %Elk County95Luzerne County: 94.1 %Luzerne County94.1Somerset County: 93.4 %Somerset County93.4Lawrence County: 93.2 %Lawrence County93.2Monroe County: 91.8 %Monroe County91.8Bucks County: 84.5 %Bucks County84.5Tioga County: 78.3 %Tioga County78.3Erie County: 77.5 %Erie County77.5Mercer County: 76.3 %Mercer County76.3Wyoming County: 75.6 %Wyoming County75.6Susquehanna County: 75.4 %Susquehanna County75.4Lackawanna County: 71.4 %Lackawanna County71.4Greene County: 68.2 %Greene County68.2Bradford County: 68 %Bradford County68Centre County: 66 %Centre County66Fayette County: 64.1 %Fayette County64.1Indiana County: 62.6 %Indiana County62.6Lycoming County: 62.4 %Lycoming County62.4Chester County: 62 %Chester County62Blair County: 61.3 %Blair County61.3Northampton County: 58.6 %Northampton County58.6Cumberland County: 57.3 %Cumberland County57.3Montgomery County: 56.7 %Montgomery County56.7Adams County: 56.6 %Adams County56.6Lehigh County: 56.1 %Lehigh County56.1Westmoreland County: 55.4 %Westmoreland County55.4Berks County: 54.2 %Berks County54.2Lebanon County: 54 %Lebanon County54Armstrong County: 52.6 %Armstrong County52.6Washington County: 51.2 %Washington County51.2Delaware County: 49.9 %Delaware County49.9Cambria County: 47.9 %Cambria County47.9York County: 47.1 %York County47.1Beaver County: 46.6 %Beaver County46.6Dauphin County: 43.2 %Dauphin County43.2Philadelphia County: 37.5 %Philadelphia County37.5Allegheny County: 32.3 %Allegheny County32.3Lancaster County: 27.4 %Lancaster County27.4
%. Source: Invokely calculation with data from EPA. Retrieved 2026-10-12.

Full ranking

RankCounties2021 (%)Change on 2020
1Clearfield County98.9-0.5 pts
2Franklin County95.1-4.9 pts
3Elk County95-4.4 pts
4Luzerne County94.1-5.3 pts
5Somerset County93.4-4.4 pts
6Lawrence County93.2-4.3 pts
7Monroe County91.8-7.6 pts
8Bucks County84.5-9.8 pts
9Tioga County78.3-6.4 pts
10Erie County77.5-4.6 pts
11Mercer County76.3+2 pts
12Wyoming County75.6-7.5 pts
13Susquehanna County75.4-9.8 pts
14Lackawanna County71.4-9.2 pts
15Greene County68.2-13.7 pts
16Bradford County68-16.1 pts
17Centre County66-12.4 pts
18Fayette County64.1-8.9 pts
19Indiana County62.6-28.6 pts
20Lycoming County62.4-14.9 pts
21Chester County62-3.6 pts
22Blair County61.3-11.5 pts
23Northampton County58.6-12.6 pts
24Cumberland County57.3-7.7 pts
25Montgomery County56.7-16.8 pts
26Adams County56.6-19.9 pts
27Lehigh County56.1-16.9 pts
28Westmoreland County55.4-22.2 pts
29Berks County54.2-8.5 pts
30Lebanon County54-14.2 pts
31Armstrong County52.6-14.6 pts
32Washington County51.2-9.2 pts
33Delaware County49.9+2.4 pts
34Cambria County47.9-14.4 pts
35York County47.1-13.3 pts
36Beaver County46.6-9.4 pts
37Dauphin County43.2-16.6 pts
38Philadelphia County37.5-20.4 pts
39Allegheny County32.3-5.4 pts
40Lancaster County27.4-21 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. 4 counties with data in other periods have no value for 2021 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), 2021) [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), 2021. 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=2021. 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), 2021. 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=2021.

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), 2021 [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=2021 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_pennsylvania_by_2021,
  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), 2021}},
  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=2021. 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), 2021
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=2021
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/pennsylvania-counties?period=2021.
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)?

Clearfield County, with 98.9% in 2021, according to EPA.

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

Lancaster County, with 27.4% in 2021.

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. 4 counties have no value for 2021 and are not ranked.

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

Counties in Pennsylvania: more rankings