Data / Rankings / Share of days with good air quality (US EPA AQI) / Counties in Michigan

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

Gratiot County had the highest share of days with good air quality (US EPA AQI) of 33 counties in 1991, at 100%. Berrien County had the lowest, at 35.4%. The median was 77%. Source: EPA.

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Highest100Gratiot County
Lowest35.4Berrien County
Median7733 counties

Map of counties, 1991

Allegan County: 36.6 %Bay County: 86.7 %Benzie County: 60.6 %Berrien County: 35.4 %Calhoun County: 88.3 %Cass County: 38.5 %Clinton County: 67.1 %Delta County: 67.3 %Dickinson County: 93.1 %Genesee County: 70.5 %Gratiot County: 100 %Houghton County: 88.5 %Ingham County: 70.1 %Kalamazoo County: 91.5 %Kent County: 79.5 %Keweenaw County: 93.5 %Macomb County: 77 %Manistee County: 81.8 %Marquette County: 96.7 %Mason County: 62.2 %Midland County: 98.4 %Monroe County: 98.1 %Montcalm County: 47.9 %Muskegon County: 63.8 %Oakland County: 80.5 %Oceana County: 48.8 %Ottawa County: 58.4 %Saginaw County: 90.8 %St. Clair County: 65.4 %Tuscola County: 79.7 %Van Buren County: 84.9 %Washtenaw County: 75.8 %Wayne County: 65.2 %
  • Under 59
  • 59 to 67
  • 67 to 77
  • 77 to 86
  • 86 to 93
  • 93 and over
  • No data
%, 1991. 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, 1991

Gratiot County: 100 %Gratiot County100Midland County: 98.4 %Midland County98.4Monroe County: 98.1 %Monroe County98.1Marquette County: 96.7 %Marquette County96.7Keweenaw County: 93.5 %Keweenaw County93.5Dickinson County: 93.1 %Dickinson County93.1Kalamazoo County: 91.5 %Kalamazoo County91.5Saginaw County: 90.8 %Saginaw County90.8Houghton County: 88.5 %Houghton County88.5Calhoun County: 88.3 %Calhoun County88.3Bay County: 86.7 %Bay County86.7Van Buren County: 84.9 %Van Buren County84.9Manistee County: 81.8 %Manistee County81.8Oakland County: 80.5 %Oakland County80.5Tuscola County: 79.7 %Tuscola County79.7Kent County: 79.5 %Kent County79.5Macomb County: 77 %Macomb County77Washtenaw County: 75.8 %Washtenaw County75.8Genesee County: 70.5 %Genesee County70.5Ingham County: 70.1 %Ingham County70.1Delta County: 67.3 %Delta County67.3Clinton County: 67.1 %Clinton County67.1St. Clair County: 65.4 %St. Clair County65.4Wayne County: 65.2 %Wayne County65.2Muskegon County: 63.8 %Muskegon County63.8Mason County: 62.2 %Mason County62.2Benzie County: 60.6 %Benzie County60.6Ottawa County: 58.4 %Ottawa County58.4Oceana County: 48.8 %Oceana County48.8Montcalm County: 47.9 %Montcalm County47.9Cass County: 38.5 %Cass County38.5Allegan County: 36.6 %Allegan County36.6Berrien County: 35.4 %Berrien County35.4Gratiot County: 100 %Gratiot County100Midland County: 98.4 %Midland County98.4Monroe County: 98.1 %Monroe County98.1Marquette County: 96.7 %Marquette County96.7Keweenaw County: 93.5 %Keweenaw County93.5Dickinson County: 93.1 %Dickinson County93.1Kalamazoo County: 91.5 %Kalamazoo County91.5Saginaw County: 90.8 %Saginaw County90.8Houghton County: 88.5 %Houghton County88.5Calhoun County: 88.3 %Calhoun County88.3Bay County: 86.7 %Bay County86.7Van Buren County: 84.9 %Van Buren County84.9Manistee County: 81.8 %Manistee County81.8Oakland County: 80.5 %Oakland County80.5Tuscola County: 79.7 %Tuscola County79.7Kent County: 79.5 %Kent County79.5Macomb County: 77 %Macomb County77Washtenaw County: 75.8 %Washtenaw County75.8Genesee County: 70.5 %Genesee County70.5Ingham County: 70.1 %Ingham County70.1Delta County: 67.3 %Delta County67.3Clinton County: 67.1 %Clinton County67.1St. Clair County: 65.4 %St. Clair County65.4Wayne County: 65.2 %Wayne County65.2Muskegon County: 63.8 %Muskegon County63.8Mason County: 62.2 %Mason County62.2Benzie County: 60.6 %Benzie County60.6Ottawa County: 58.4 %Ottawa County58.4Oceana County: 48.8 %Oceana County48.8Montcalm County: 47.9 %Montcalm County47.9Cass County: 38.5 %Cass County38.5Allegan County: 36.6 %Allegan County36.6Berrien County: 35.4 %Berrien County35.4
%. Source: Invokely calculation with data from EPA. Retrieved 2026-10-12.

Full ranking

RankCounties1991 (%)Change on 1990
1Gratiot County1000 pts
2Midland County98.4+0.7 pts
3Monroe County98.1+13.1 pts
4Marquette County96.7+1.6 pts
5Keweenaw County93.5+5.1 pts
6Dickinson County93.1-1.1 pts
7Kalamazoo County91.5n/a
8Saginaw County90.8-4.8 pts
9Houghton County88.5-7.9 pts
10Calhoun County88.3-1.3 pts
11Bay County86.7-4.8 pts
12Van Buren County84.9n/a
13Manistee County81.8-4.6 pts
14Oakland County80.5-9.9 pts
15Tuscola County79.70 pts
16Kent County79.5-1 pts
17Macomb County77-4.4 pts
18Washtenaw County75.8-3 pts
19Genesee County70.5-4.7 pts
20Ingham County70.1-7.4 pts
21Delta County67.3n/a
22Clinton County67.1-6.7 pts
23St. Clair County65.4-6.6 pts
24Wayne County65.2+7.1 pts
25Muskegon County63.8-3.4 pts
26Mason County62.2-19.6 pts
27Benzie County60.6n/a
28Ottawa County58.4-10.8 pts
29Oceana County48.8n/a
30Montcalm County47.9n/a
31Cass County38.5n/a
32Allegan County36.6-13.4 pts
33Berrien County35.4n/a

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. 20 counties with data in other periods have no value for 1991 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), 1991) [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), 1991. 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=1991. 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), 1991. 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=1991.

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), 1991 [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=1991 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_michigan_by_1991,
  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), 1991}},
  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=1991. 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), 1991
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=1991
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/michigan-counties?period=1991.
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)?

Gratiot County, with 100% in 1991, according to EPA.

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

Berrien County, with 35.4% in 1991.

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. 20 counties have no value for 1991 and are not ranked.

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

Counties in Michigan: more rankings