EnviroNearby

Cass County, Michigan air quality history

Daily Air Quality Index summaries from EPA monitors in Cass, Michigan, 1980–2025.

85%
Good days in 2025
40
Median daily AQI, 2025
2
Days above 100 in 2025
224
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Cass, Michigan on 224 days. 191 of those days (85%) were in the Good range, and the median daily AQI was 40. That median is about the same as the typical monitored county in Michigan (median 39 across 26 counties), and about the same as the typical monitored U.S. county (40). The main pollutant was ozone on 224 days. Across the years with fuller monitoring, the share of Good days rose: an average of 76% in 1980–1983 versus 82% in 2023–2025.

EPA did not report an AQI for every day of 2025 here (224 of 365 days). Figures describe monitored days only; seasonal monitoring (for example, ozone measured only in warmer months) can make a county look cleaner or dirtier than a full-year record would.

Years with fewer than 120 monitored days (1981, 2003) are shown in the table but left out of comparisons and trend statements.

How the days broke down each year

Each bar is one year. The colored segments show the share of monitored days that fell in each AQI category.

Share of monitored days in each AQI category, by year0%25%50%75%100%1980: Good 111 of 158 days1980: Moderate 24 of 158 days1980: Unhealthy for Sensitive Groups 17 of 158 days1980: Unhealthy 4 of 158 days1980: Very Unhealthy 2 of 158 days19801981: Good 46 of 49 days1981: Moderate 3 of 49 days1982: Good 166 of 207 days1982: Moderate 35 of 207 days1982: Unhealthy for Sensitive Groups 6 of 207 days1983: Good 138 of 176 days1983: Moderate 22 of 176 days1983: Unhealthy for Sensitive Groups 12 of 176 days1983: Unhealthy 3 of 176 days1983: Very Unhealthy 1 of 176 days1984: Good 172 of 197 days1984: Moderate 21 of 197 days1984: Unhealthy for Sensitive Groups 4 of 197 days1985: Good 160 of 199 days1985: Moderate 31 of 199 days1985: Unhealthy for Sensitive Groups 6 of 199 days1985: Unhealthy 2 of 199 days19851991: Good 50 of 130 days1991: Moderate 30 of 130 days1991: Unhealthy for Sensitive Groups 39 of 130 days1991: Unhealthy 10 of 130 days1991: Very Unhealthy 1 of 130 days1992: Good 103 of 162 days1992: Moderate 39 of 162 days1992: Unhealthy for Sensitive Groups 13 of 162 days1992: Unhealthy 7 of 162 days1993: Good 120 of 183 days1993: Moderate 48 of 183 days1993: Unhealthy for Sensitive Groups 14 of 183 days1993: Unhealthy 1 of 183 days1994: Good 96 of 182 days1994: Moderate 54 of 182 days1994: Unhealthy for Sensitive Groups 23 of 182 days1994: Unhealthy 8 of 182 days1994: Very Unhealthy 1 of 182 days1995: Good 92 of 176 days1995: Moderate 51 of 176 days1995: Unhealthy for Sensitive Groups 19 of 176 days1995: Unhealthy 13 of 176 days1995: Very Unhealthy 1 of 176 days19951996: Good 95 of 183 days1996: Moderate 57 of 183 days1996: Unhealthy for Sensitive Groups 19 of 183 days1996: Unhealthy 12 of 183 days1997: Good 108 of 170 days1997: Moderate 42 of 170 days1997: Unhealthy for Sensitive Groups 13 of 170 days1997: Unhealthy 7 of 170 days1998: Good 63 of 170 days1998: Moderate 70 of 170 days1998: Unhealthy for Sensitive Groups 30 of 170 days1998: Unhealthy 7 of 170 days1999: Good 70 of 148 days1999: Moderate 43 of 148 days1999: Unhealthy for Sensitive Groups 22 of 148 days1999: Unhealthy 12 of 148 days1999: Very Unhealthy 1 of 148 days2000: Good 114 of 168 days2000: Moderate 44 of 168 days2000: Unhealthy for Sensitive Groups 7 of 168 days2000: Unhealthy 3 of 168 days20002001: Good 101 of 162 days2001: Moderate 41 of 162 days2001: Unhealthy for Sensitive Groups 14 of 162 days2001: Unhealthy 6 of 162 days2002: Good 81 of 164 days2002: Moderate 42 of 164 days2002: Unhealthy for Sensitive Groups 18 of 164 days2002: Unhealthy 21 of 164 days2002: Very Unhealthy 2 of 164 days2003: Good 53 of 100 days2003: Moderate 36 of 100 days2003: Unhealthy for Sensitive Groups 6 of 100 days2003: Unhealthy 5 of 100 days2004: Good 121 of 171 days2004: Moderate 41 of 171 days2004: Unhealthy for Sensitive Groups 9 of 171 days2005: Good 79 of 183 days2005: Moderate 75 of 183 days2005: Unhealthy for Sensitive Groups 25 of 183 days2005: Unhealthy 4 of 183 days20052006: Good 130 of 182 days2006: Moderate 45 of 182 days2006: Unhealthy for Sensitive Groups 7 of 182 days2007: Good 109 of 183 days2007: Moderate 60 of 183 days2007: Unhealthy for Sensitive Groups 11 of 183 days2007: Unhealthy 3 of 183 days2008: Good 124 of 183 days2008: Moderate 55 of 183 days2008: Unhealthy for Sensitive Groups 4 of 183 days2009: Good 134 of 183 days2009: Moderate 45 of 183 days2009: Unhealthy for Sensitive Groups 4 of 183 days2010: Good 133 of 180 days2010: Moderate 44 of 180 days2010: Unhealthy for Sensitive Groups 3 of 180 days20102011: Good 130 of 177 days2011: Moderate 35 of 177 days2011: Unhealthy for Sensitive Groups 11 of 177 days2011: Unhealthy 1 of 177 days2012: Good 105 of 177 days2012: Moderate 49 of 177 days2012: Unhealthy for Sensitive Groups 20 of 177 days2012: Unhealthy 1 of 177 days2012: Very Unhealthy 2 of 177 days2013: Good 128 of 183 days2013: Moderate 51 of 183 days2013: Unhealthy for Sensitive Groups 4 of 183 days2014: Good 120 of 167 days2014: Moderate 46 of 167 days2014: Unhealthy for Sensitive Groups 1 of 167 days2015: Good 141 of 180 days2015: Moderate 37 of 180 days2015: Unhealthy for Sensitive Groups 2 of 180 days20152016: Good 128 of 183 days2016: Moderate 46 of 183 days2016: Unhealthy for Sensitive Groups 9 of 183 days2017: Good 198 of 245 days2017: Moderate 41 of 245 days2017: Unhealthy for Sensitive Groups 6 of 245 days2018: Good 202 of 240 days2018: Moderate 31 of 240 days2018: Unhealthy for Sensitive Groups 7 of 240 days2019: Good 229 of 255 days2019: Moderate 26 of 255 days2020: Good 212 of 253 days2020: Moderate 36 of 253 days2020: Unhealthy for Sensitive Groups 5 of 253 days20202021: Good 235 of 265 days2021: Moderate 29 of 265 days2021: Unhealthy for Sensitive Groups 1 of 265 days2022: Good 212 of 233 days2022: Moderate 19 of 233 days2022: Unhealthy for Sensitive Groups 2 of 233 days2023: Good 190 of 244 days2023: Moderate 45 of 244 days2023: Unhealthy for Sensitive Groups 9 of 244 days2024: Good 205 of 251 days2024: Moderate 45 of 251 days2024: Unhealthy for Sensitive Groups 1 of 251 days2025: Good 191 of 224 days2025: Moderate 31 of 224 days2025: Unhealthy for Sensitive Groups 2 of 224 days2025
  • Good
  • Moderate
  • Unhealthy for Sensitive Groups
  • Unhealthy
  • Very Unhealthy
  • Hazardous

Typical and high-end AQI over time

The median is the middle day of the year. The 90th percentile is the level that only the highest 10% of days exceeded.

Median and 90th-percentile daily AQI, by year0501001502001980: 90th percentile AQI 1151981: 90th percentile AQI 461982: 90th percentile AQI 711983: 90th percentile AQI 1001984: 90th percentile AQI 581985: 90th percentile AQI 711991: 90th percentile AQI 1471992: 90th percentile AQI 1151993: 90th percentile AQI 971994: 90th percentile AQI 1191995: 90th percentile AQI 1471996: 90th percentile AQI 1261997: 90th percentile AQI 1121998: 90th percentile AQI 1331999: 90th percentile AQI 1472000: 90th percentile AQI 872001: 90th percentile AQI 1082002: 90th percentile AQI 1592003: 90th percentile AQI 1012004: 90th percentile AQI 772005: 90th percentile AQI 1122006: 90th percentile AQI 742007: 90th percentile AQI 1002008: 90th percentile AQI 802009: 90th percentile AQI 672010: 90th percentile AQI 672011: 90th percentile AQI 932012: 90th percentile AQI 1122013: 90th percentile AQI 742014: 90th percentile AQI 712015: 90th percentile AQI 712016: 90th percentile AQI 872017: 90th percentile AQI 642018: 90th percentile AQI 642019: 90th percentile AQI 512020: 90th percentile AQI 612021: 90th percentile AQI 542022: 90th percentile AQI 502023: 90th percentile AQI 712024: 90th percentile AQI 582025: 90th percentile AQI 611980: Median AQI 411981: Median AQI 301982: Median AQI 371983: Median AQI 381984: Median AQI 331985: Median AQI 391991: Median AQI 711992: Median AQI 451993: Median AQI 441994: Median AQI 491995: Median AQI 501996: Median AQI 501997: Median AQI 451998: Median AQI 611999: Median AQI 542000: Median AQI 442001: Median AQI 442002: Median AQI 542003: Median AQI 492004: Median AQI 442005: Median AQI 582006: Median AQI 452007: Median AQI 482008: Median AQI 442009: Median AQI 442010: Median AQI 452011: Median AQI 442012: Median AQI 462013: Median AQI 452014: Median AQI 442015: Median AQI 442016: Median AQI 422017: Median AQI 412018: Median AQI 402019: Median AQI 392020: Median AQI 392021: Median AQI 402022: Median AQI 382023: Median AQI 422024: Median AQI 422025: Median AQI 40198019851995200020052010201520202025
  • Median daily AQI
  • 90th-percentile daily AQI

Main pollutant by day, 2025

On each monitored day, the AQI reflects whichever measured pollutant had the highest index. This counts how many days each pollutant set the AQI. A pollutant that was not measured here cannot appear.

PollutantDays as main pollutantShare of monitored days
Ozone224100%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
20252241913120004061115Ozone
20242512054510004258108Ozone
20232441904590004271126Ozone
20222332121920003850119Ozone
20212652352910004054112Ozone
20202532123650003961122Ozone
2019255229260000395190Ozone
20182402023170004064126Ozone
20172451984160004164126Ozone
20161831284690004287129Ozone
20151801413720004471126Ozone
20141671204610004471115Ozone
20131831285140004574122Ozone
2012177105492012046112203Ozone
201117713035111004493154Ozone
20101801334430004567108Ozone
20091831344540004467129Ozone
20081831245540004480115Ozone
2007183109601130048100151Ozone
20061821304570004574133Ozone
200518379752540058112164Ozone
20041711214190004477143Ozone
20031005336650049101190Ozone
2002164814218212054159212Ozone
2001162101411460044108164Ozone
20001681144473004487166Ozone
1999148704322121054147201Ozone
199817063703070061133192Ozone
1997170108421370045112190Ozone
1996183955719120050126200Ozone
1995176925119131050147206Ozone
199418296542381049119201Ozone
199318312048141004497166Ozone
1992162103391370045115187Ozone
1991130503039101071147207Ozone
19851991603162003971164Ozone
19841971722140003358140Ozone
1983176138221231038100202Ozone
19822071663560003771126Ozone
1981494630000304674Ozone
1980158111241742041115205Ozone

What this data can and can’t tell you

It is a county-level summary. EPA reports one AQI per day for the county, based on the monitors operating there. Air at a particular street, school or home can differ, especially near roads, industry or wildfire smoke.

It is not a health assessment. The AQI is EPA’s scale for communicating daily air quality. A county’s history can’t tell you what the health risk is for any particular person. For daily conditions and health guidance, see AirNow.

Rules change over time. EPA has revised AQI breakpoints, most recently for fine particles in 2024, so some year-to-year change can reflect the scale rather than the air.

Counties in Michigan with a similar median AQI in 2025

All monitored counties in Michigan

Source: U.S. EPA AirData, “Annual AQI by County” files for 1980–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem