Counties in Pennsylvania by highest daily Air Quality Index (US EPA)

Northampton County had the highest highest daily Air Quality Index (US EPA) of 37 counties in 2016, at 242. Franklin County had the lowest, at 74. The median was 126. Source: the U.S. Environmental Protection Agency.

Highest242Northampton County

Lowest74Franklin County

Median12637 counties

Map of counties, 2016

Under 110
110 to 120
120 to 130
130 to 140
140 and over
No data

index, 2016. Hatched areas have no value for this period. Source: EPA, EPA AirData annual AQI by county: highest daily AQI. Boundaries: U.S. Census Bureau cartographic boundary files.

All counties, 2016

index. Source: EPA, EPA AirData annual AQI by county: highest daily AQI. Retrieved 2026-10-12.

Full ranking

Rank	Counties	2016 index	Change on 2015
1	Northampton County	242	+123
2	Allegheny County	152	-5
3	Bucks County	147	-17
3	Philadelphia County	147	-14
5	Chester County	143	-23
5	Mercer County	143	-10
7	Monroe County	140	+28
7	Montgomery County	140	+7
9	Delaware County	136	-14
9	Indiana County	136	+17
9	Lancaster County	136	-4
12	York County	133	+7
13	Berks County	129	+10
13	Erie County	129	+14
13	Lackawanna County	129	+21
13	Lehigh County	129	+21
13	Washington County	129	+10
18	Beaver County	126	+4
18	Elk County	126	+25
20	Blair County	122	+14
20	Centre County	122	+14
20	Lebanon County	122	-11
23	Adams County	119	+18
23	Armstrong County	119	+4
23	Clearfield County	119	+19
23	Luzerne County	119	+14
27	Cumberland County	116	-5
28	Dauphin County	115	-9
29	Lawrence County	112	+11
29	Tioga County	112	+22
29	Westmoreland County	112	-35
32	Lycoming County	108	+21
33	Greene County	105	-10
33	Somerset County	105	+28
35	Bradford County	97	+20
35	Cambria County	97	0
37	Franklin County	74	-3

Other periods

About this ranking

Highest daily Air Quality Index (AQI) value recorded in a US county during the year, from the EPA AirData annual summaries. Values above 500 are beyond the AQI scale and are published as EPA computes them.

A single day decides the value, so one wildfire or dust event can set it. Dust from the dry Owens Lake bed puts Inyo and Mono counties in California in the thousands. 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 2016 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: highest daily AQI. 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: highest daily AQI (Counties in Pennsylvania by highest daily Air Quality Index (US EPA), 2016) [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: highest daily AQI, Counties in Pennsylvania by highest daily Air Quality Index (US EPA), 2016. U.S. Environmental Protection Agency, 13 July 2026, https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Invokely, https://invokely.ai/rankings/highest-daily-air-quality-index/pennsylvania-counties?period=2016. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Environmental Protection Agency. 2026. EPA AirData annual AQI by county: highest daily AQI. Counties in Pennsylvania by highest daily Air Quality Index (US EPA), 2016. Dataset. Accessed October 12, 2026. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Also distributed by Invokely, https://invokely.ai/rankings/highest-daily-air-quality-index/pennsylvania-counties?period=2016.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: highest daily AQI, Counties in Pennsylvania by highest daily Air Quality Index (US EPA), 2016 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/rankings/highest-daily-air-quality-index/pennsylvania-counties?period=2016 (Accessed: 12 October 2026).

BibTeX

@misc{environmental_counties_in_pennsylvania_by_2016,
  author = {{U.S. Environmental Protection Agency}},
  title = {{EPA AirData annual AQI by county: highest daily AQI: Counties in Pennsylvania by highest daily Air Quality Index (US EPA), 2016}},
  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/highest-daily-air-quality-index/pennsylvania-counties?period=2016. Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: highest daily AQI. 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: highest daily AQI: Counties in Pennsylvania by highest daily Air Quality Index (US EPA), 2016
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/highest-daily-air-quality-index/pennsylvania-counties?period=2016
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/highest-daily-air-quality-index/pennsylvania-counties?period=2016.
N1  - Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: highest daily AQI. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Retrieved 2026-10-12.
ER  -

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Rank Counties in Pennsylvania by highest daily Air Quality Index (US EPA) using official data, and cite the source.

rank_places {"indicator":"aqi_max","level":"province","within":"Pennsylvania","limit":10}
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Questions

Which county has the highest highest daily Air Quality Index (US EPA)?

Northampton County, with 242 in 2016, according to the U.S. Environmental Protection Agency.

Which county has the lowest highest daily Air Quality Index (US EPA)?

Franklin County, with 74 in 2016.

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: highest daily AQI. Retrieved 2026-10-12. 7 counties have no value for 2016 and are not ranked.