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

Cheboygan County had the highest share of days with good air quality (US EPA AQI) of 30 counties in 1994, at 100%. Cass County had the lowest, at 52.7%. The median was 77.7%. Source: EPA.

Highest100Cheboygan County

Lowest52.7Cass County

Median77.730 counties

Map of counties, 1994

Under 64
64 to 73
73 to 78
78 to 85
85 to 97
97 and over
No data

%, 1994. 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, 1994

%. Source: Invokely calculation with data from EPA. Retrieved 2026-10-12.

Full ranking

Rank	Counties	1994 (%)	Change on 1993
1	Cheboygan County	100	0 pts
1	Gratiot County	100	0 pts
1	Marquette County	100	+1.6 pts
1	Saginaw County	100	+1.6 pts
5	Van Buren County	98.9	-1.1 pts
6	Calhoun County	96.6	-0.1 pts
7	Monroe County	96.4	+12 pts
7	Sanilac County	96.4	-3.6 pts
9	Midland County	95	-2.8 pts
10	Oakland County	86.4	-4.4 pts
11	Manistee County	84.2	-6.7 pts
12	Tuscola County	83.1	-8.4 pts
13	Kent County	81.9	-4.9 pts
13	Macomb County	81.9	-5.5 pts
15	Washtenaw County	78.2	-7.5 pts
16	Genesee County	77.1	-4.6 pts
17	Kalamazoo County	76.7	-3.8 pts
18	Ingham County	76.4	-7.8 pts
19	Huron County	75.1	-6.7 pts
20	Clinton County	73.2	-8.6 pts
21	St. Clair County	71.6	-2.2 pts
22	Mason County	67.7	-2.1 pts
23	Benzie County	67.2	-14.7 pts
24	Berrien County	66.7	-3.6 pts
25	Ottawa County	64.8	n/a
26	Muskegon County	62.8	-12.5 pts
27	Allegan County	62.4	-7.3 pts
28	Lenawee County	58.2	-10.4 pts
29	Wayne County	53.7	-9.9 pts
30	Cass County	52.7	-12.9 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. 23 counties with data in other periods have no value for 1994 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 Michigan by share of days with good air quality (US EPA AQI), 1994) [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 Michigan by share of days with good air quality (US EPA AQI), 1994. 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/michigan-counties?period=1994. 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 Michigan by share of days with good air quality (US EPA AQI), 1994. 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/michigan-counties?period=1994.

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 Michigan by share of days with good air quality (US EPA AQI), 1994 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/rankings/good-air-quality-days-share/michigan-counties?period=1994 (Accessed: 12 October 2026).

BibTeX

@misc{environmental_counties_in_michigan_by_1994,
  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 Michigan by share of days with good air quality (US EPA AQI), 1994}},
  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/michigan-counties?period=1994. 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 Michigan by share of days with good air quality (US EPA AQI), 1994
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/michigan-counties?period=1994
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/michigan-counties?period=1994.
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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Rank Counties in Michigan by share of days with good air quality (US EPA AQI) using official data, and cite the source.

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Questions

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

Cheboygan County, with 100% in 1994, according to EPA.

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

Cass County, with 52.7% in 1994.

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. 23 counties have no value for 1994 and are not ranked.