EnviroNearby

St. Clair County, Michigan air quality history

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

70%
Good days in 2025
39
Median daily AQI, 2025
11
Days above 100 in 2025
365
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for St. Clair, Michigan on 365 days. 254 of those days (70%) were in the Good range, and the median daily AQI was 39. 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 fine particles (PM2.5) on 191 days. Across the years with fuller monitoring, the share of Good days fell: an average of 82% in 1980–1982 versus 64% in 2023–2025.

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 306 of 365 days1980: Moderate 41 of 365 days1980: Unhealthy for Sensitive Groups 16 of 365 days1980: Unhealthy 2 of 365 days19801981: Good 304 of 362 days1981: Moderate 31 of 362 days1981: Unhealthy for Sensitive Groups 16 of 362 days1981: Unhealthy 8 of 362 days1981: Very Unhealthy 3 of 362 days1982: Good 276 of 353 days1982: Moderate 58 of 353 days1982: Unhealthy for Sensitive Groups 10 of 353 days1982: Unhealthy 8 of 353 days1982: Very Unhealthy 1 of 353 days1983: Good 121 of 177 days1983: Moderate 29 of 177 days1983: Unhealthy for Sensitive Groups 12 of 177 days1983: Unhealthy 8 of 177 days1983: Very Unhealthy 7 of 177 days1984: Good 141 of 184 days1984: Moderate 26 of 184 days1984: Unhealthy for Sensitive Groups 13 of 184 days1984: Unhealthy 3 of 184 days1984: Very Unhealthy 1 of 184 days1985: Good 140 of 196 days1985: Moderate 35 of 196 days1985: Unhealthy for Sensitive Groups 17 of 196 days1985: Unhealthy 4 of 196 days19851986: Good 164 of 197 days1986: Moderate 22 of 197 days1986: Unhealthy for Sensitive Groups 4 of 197 days1986: Unhealthy 7 of 197 days1987: Good 152 of 206 days1987: Moderate 32 of 206 days1987: Unhealthy for Sensitive Groups 15 of 206 days1987: Unhealthy 6 of 206 days1987: Very Unhealthy 1 of 206 days1988: Good 142 of 203 days1988: Moderate 27 of 203 days1988: Unhealthy for Sensitive Groups 10 of 203 days1988: Unhealthy 20 of 203 days1988: Very Unhealthy 4 of 203 days1989: Good 156 of 211 days1989: Moderate 29 of 211 days1989: Unhealthy for Sensitive Groups 15 of 211 days1989: Unhealthy 10 of 211 days1989: Very Unhealthy 1 of 211 days1990: Good 154 of 214 days1990: Moderate 38 of 214 days1990: Unhealthy for Sensitive Groups 17 of 214 days1990: Unhealthy 4 of 214 days1990: Very Unhealthy 1 of 214 days19901991: Good 140 of 214 days1991: Moderate 34 of 214 days1991: Unhealthy for Sensitive Groups 22 of 214 days1991: Unhealthy 13 of 214 days1991: Very Unhealthy 5 of 214 days1992: Good 148 of 183 days1992: Moderate 25 of 183 days1992: Unhealthy for Sensitive Groups 6 of 183 days1992: Unhealthy 4 of 183 days1993: Good 135 of 183 days1993: Moderate 33 of 183 days1993: Unhealthy for Sensitive Groups 11 of 183 days1993: Unhealthy 4 of 183 days1994: Good 131 of 183 days1994: Moderate 23 of 183 days1994: Unhealthy for Sensitive Groups 22 of 183 days1994: Unhealthy 5 of 183 days1994: Very Unhealthy 2 of 183 days1995: Good 124 of 183 days1995: Moderate 41 of 183 days1995: Unhealthy for Sensitive Groups 10 of 183 days1995: Unhealthy 6 of 183 days1995: Very Unhealthy 2 of 183 days19951996: Good 121 of 183 days1996: Moderate 40 of 183 days1996: Unhealthy for Sensitive Groups 13 of 183 days1996: Unhealthy 9 of 183 days1997: Good 130 of 183 days1997: Moderate 33 of 183 days1997: Unhealthy for Sensitive Groups 14 of 183 days1997: Unhealthy 6 of 183 days1998: Good 118 of 179 days1998: Moderate 37 of 179 days1998: Unhealthy for Sensitive Groups 15 of 179 days1998: Unhealthy 8 of 179 days1998: Very Unhealthy 1 of 179 days1999: Good 134 of 234 days1999: Moderate 76 of 234 days1999: Unhealthy for Sensitive Groups 16 of 234 days1999: Unhealthy 8 of 234 days2000: Good 142 of 226 days2000: Moderate 77 of 226 days2000: Unhealthy for Sensitive Groups 5 of 226 days2000: Unhealthy 2 of 226 days20002001: Good 135 of 241 days2001: Moderate 83 of 241 days2001: Unhealthy for Sensitive Groups 21 of 241 days2001: Unhealthy 2 of 241 days2002: Good 126 of 242 days2002: Moderate 90 of 242 days2002: Unhealthy for Sensitive Groups 11 of 242 days2002: Unhealthy 14 of 242 days2002: Very Unhealthy 1 of 242 days2003: Good 138 of 235 days2003: Moderate 82 of 235 days2003: Unhealthy for Sensitive Groups 9 of 235 days2003: Unhealthy 5 of 235 days2003: Very Unhealthy 1 of 235 days2004: Good 162 of 237 days2004: Moderate 67 of 237 days2004: Unhealthy for Sensitive Groups 8 of 237 days2005: Good 143 of 242 days2005: Moderate 78 of 242 days2005: Unhealthy for Sensitive Groups 15 of 242 days2005: Unhealthy 5 of 242 days2005: Very Unhealthy 1 of 242 days20052006: Good 156 of 229 days2006: Moderate 61 of 229 days2006: Unhealthy for Sensitive Groups 11 of 229 days2006: Unhealthy 1 of 229 days2007: Good 143 of 241 days2007: Moderate 78 of 241 days2007: Unhealthy for Sensitive Groups 16 of 241 days2007: Unhealthy 4 of 241 days2008: Good 150 of 241 days2008: Moderate 88 of 241 days2008: Unhealthy for Sensitive Groups 3 of 241 days2009: Good 168 of 241 days2009: Moderate 69 of 241 days2009: Unhealthy for Sensitive Groups 4 of 241 days2010: Good 161 of 243 days2010: Moderate 71 of 243 days2010: Unhealthy for Sensitive Groups 11 of 243 days20102011: Good 168 of 242 days2011: Moderate 65 of 242 days2011: Unhealthy for Sensitive Groups 8 of 242 days2011: Unhealthy 1 of 242 days2012: Good 146 of 243 days2012: Moderate 82 of 243 days2012: Unhealthy for Sensitive Groups 14 of 243 days2012: Very Unhealthy 1 of 243 days2013: Good 171 of 244 days2013: Moderate 67 of 244 days2013: Unhealthy for Sensitive Groups 6 of 244 days2014: Good 187 of 365 days2014: Moderate 173 of 365 days2014: Unhealthy for Sensitive Groups 5 of 365 days2015: Good 198 of 363 days2015: Moderate 155 of 363 days2015: Unhealthy for Sensitive Groups 10 of 363 days20152016: Good 236 of 364 days2016: Moderate 124 of 364 days2016: Unhealthy for Sensitive Groups 4 of 364 days2017: Good 232 of 358 days2017: Moderate 124 of 358 days2017: Unhealthy for Sensitive Groups 2 of 358 days2018: Good 200 of 310 days2018: Moderate 103 of 310 days2018: Unhealthy for Sensitive Groups 6 of 310 days2018: Unhealthy 1 of 310 days2019: Good 266 of 365 days2019: Moderate 96 of 365 days2019: Unhealthy for Sensitive Groups 3 of 365 days2020: Good 247 of 328 days2020: Moderate 80 of 328 days2020: Unhealthy for Sensitive Groups 1 of 328 days20202021: Good 198 of 365 days2021: Moderate 160 of 365 days2021: Unhealthy for Sensitive Groups 7 of 365 days2022: Good 232 of 359 days2022: Moderate 125 of 359 days2022: Unhealthy for Sensitive Groups 2 of 359 days2023: Good 186 of 362 days2023: Moderate 163 of 362 days2023: Unhealthy for Sensitive Groups 9 of 362 days2023: Unhealthy 4 of 362 days2024: Good 261 of 360 days2024: Moderate 96 of 360 days2024: Unhealthy for Sensitive Groups 3 of 360 days2025: Good 254 of 365 days2025: Moderate 100 of 365 days2025: Unhealthy for Sensitive Groups 10 of 365 days2025: Unhealthy 1 of 365 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 641981: 90th percentile AQI 731982: 90th percentile AQI 741983: 90th percentile AQI 1431984: 90th percentile AQI 971985: 90th percentile AQI 1011986: 90th percentile AQI 771987: 90th percentile AQI 1081988: 90th percentile AQI 1511989: 90th percentile AQI 1151990: 90th percentile AQI 1011991: 90th percentile AQI 1431992: 90th percentile AQI 841993: 90th percentile AQI 971994: 90th percentile AQI 1151995: 90th percentile AQI 1001996: 90th percentile AQI 1051997: 90th percentile AQI 1011998: 90th percentile AQI 1191999: 90th percentile AQI 1012000: 90th percentile AQI 782001: 90th percentile AQI 972002: 90th percentile AQI 1052003: 90th percentile AQI 862004: 90th percentile AQI 802005: 90th percentile AQI 932006: 90th percentile AQI 822007: 90th percentile AQI 872008: 90th percentile AQI 742009: 90th percentile AQI 692010: 90th percentile AQI 762011: 90th percentile AQI 742012: 90th percentile AQI 872013: 90th percentile AQI 642014: 90th percentile AQI 662015: 90th percentile AQI 672016: 90th percentile AQI 612017: 90th percentile AQI 632018: 90th percentile AQI 642019: 90th percentile AQI 602020: 90th percentile AQI 602021: 90th percentile AQI 712022: 90th percentile AQI 672023: 90th percentile AQI 712024: 90th percentile AQI 642025: 90th percentile AQI 671980: Median AQI 281981: Median AQI 341982: Median AQI 331983: Median AQI 371984: Median AQI 341985: Median AQI 381986: Median AQI 331987: Median AQI 361988: Median AQI 331989: Median AQI 391990: Median AQI 401991: Median AQI 401992: Median AQI 371993: Median AQI 411994: Median AQI 421995: Median AQI 431996: Median AQI 421997: Median AQI 401998: Median AQI 421999: Median AQI 462000: Median AQI 412001: Median AQI 462002: Median AQI 482003: Median AQI 442004: Median AQI 382005: Median AQI 452006: Median AQI 402007: Median AQI 442008: Median AQI 432009: Median AQI 412010: Median AQI 422011: Median AQI 402012: Median AQI 442013: Median AQI 402014: Median AQI 492015: Median AQI 482016: Median AQI 432017: Median AQI 442018: Median AQI 442019: Median AQI 412020: Median AQI 392021: Median AQI 482022: Median AQI 432023: Median AQI 492024: Median AQI 412025: Median AQI 391980198519901995200020052010201520202025
  • 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
Fine particles (PM2.5)19152%
Ozone17448%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
2025365254100101003967152PM2.5
20243602619630004164134PM2.5
202336218616394004971197PM2.5
202235923212520004367133PM2.5
202136519816070004871140PM2.5
20203282478010003960105PM2.5
20193652669630004160108PM2.5
201831020010361004464151PM2.5
201735823212420004463112PM2.5
201636423612440004361140PM2.5
2015363198155100004867126PM2.5
201436518717350004966116PM2.5
20132441716760004064146Ozone
201224314682140104487202Ozone
20112421686581004074159Ozone
201024316171110004276150Ozone
20092411686940004169115Ozone
20082411508830004374122Ozone
200724114378164004487177Ozone
200622915661111004082161Ozone
200524214378155104593202Ozone
20042371626780003880129Ozone
20032351388295104486219Ozone
20022421269011141048105209Ozone
200124113583212004697200Ozone
20002261427752004178185Ozone
1999234134761680046101197Ozone
1998179118371581042119202Ozone
1997183130331460040101190Ozone
1996183121401390042105175Ozone
1995183124411062043100204Ozone
1994183131232252042115202Ozone
199318313533114004197177Ozone
19921831482564003784182Ozone
19912141403422135040143210Ozone
1990214154381741040101203Ozone
19892111562915101039115215Ozone
19882031422710204033151208Ozone
1987206152321561036108209Ozone
19861971642247003377195Ozone
1985196140351740038101182Ozone
198418414126133103497201Ozone
1983177121291287037143208Ozone
198235327658108103374213NO2
198136230431168303473214Ozone
198036530641162002864190Ozone

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