EnviroNearby

Clay County, Missouri air quality history

Daily Air Quality Index summaries from EPA monitors in Clay, Missouri, 1980–2025.

74%
Good days in 2025
42
Median daily AQI, 2025
7
Days above 100 in 2025
363
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Clay, Missouri on 363 days. 270 of those days (74%) were in the Good range, and the median daily AQI was 42. That median is about the same as the typical monitored county in Missouri (median 41 across 19 counties), and about the same as the typical monitored U.S. county (40). The main pollutant was ozone on 213 days. Across the years with fuller monitoring, the share of Good days rose: an average of 57% in 1980–1982 versus 73% 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 175 of 366 days1980: Moderate 140 of 366 days1980: Unhealthy for Sensitive Groups 24 of 366 days1980: Unhealthy 21 of 366 days1980: Very Unhealthy 6 of 366 days19801981: Good 213 of 365 days1981: Moderate 118 of 365 days1981: Unhealthy for Sensitive Groups 23 of 365 days1981: Unhealthy 10 of 365 days1981: Very Unhealthy 1 of 365 days1982: Good 239 of 365 days1982: Moderate 106 of 365 days1982: Unhealthy for Sensitive Groups 18 of 365 days1982: Unhealthy 2 of 365 days1983: Good 239 of 365 days1983: Moderate 84 of 365 days1983: Unhealthy for Sensitive Groups 29 of 365 days1983: Unhealthy 12 of 365 days1983: Very Unhealthy 1 of 365 days1984: Good 225 of 366 days1984: Moderate 95 of 366 days1984: Unhealthy for Sensitive Groups 29 of 366 days1984: Unhealthy 14 of 366 days1984: Very Unhealthy 3 of 366 days1985: Good 262 of 365 days1985: Moderate 78 of 365 days1985: Unhealthy for Sensitive Groups 17 of 365 days1985: Unhealthy 6 of 365 days1985: Very Unhealthy 2 of 365 days19851986: Good 277 of 365 days1986: Moderate 74 of 365 days1986: Unhealthy for Sensitive Groups 12 of 365 days1986: Unhealthy 2 of 365 days1987: Good 221 of 365 days1987: Moderate 102 of 365 days1987: Unhealthy for Sensitive Groups 35 of 365 days1987: Unhealthy 7 of 365 days1988: Good 222 of 366 days1988: Moderate 86 of 366 days1988: Unhealthy for Sensitive Groups 39 of 366 days1988: Unhealthy 16 of 366 days1988: Very Unhealthy 3 of 366 days1989: Good 259 of 365 days1989: Moderate 90 of 365 days1989: Unhealthy for Sensitive Groups 15 of 365 days1989: Unhealthy 1 of 365 days1990: Good 270 of 365 days1990: Moderate 80 of 365 days1990: Unhealthy for Sensitive Groups 13 of 365 days1990: Unhealthy 2 of 365 days19901991: Good 246 of 365 days1991: Moderate 86 of 365 days1991: Unhealthy for Sensitive Groups 25 of 365 days1991: Unhealthy 8 of 365 days1992: Good 271 of 366 days1992: Moderate 78 of 366 days1992: Unhealthy for Sensitive Groups 16 of 366 days1992: Unhealthy 1 of 366 days1993: Good 283 of 365 days1993: Moderate 63 of 365 days1993: Unhealthy for Sensitive Groups 16 of 365 days1993: Unhealthy 3 of 365 days1994: Good 246 of 365 days1994: Moderate 78 of 365 days1994: Unhealthy for Sensitive Groups 34 of 365 days1994: Unhealthy 7 of 365 days1995: Good 249 of 365 days1995: Moderate 80 of 365 days1995: Unhealthy for Sensitive Groups 19 of 365 days1995: Unhealthy 15 of 365 days1995: Very Unhealthy 2 of 365 days19951996: Good 273 of 366 days1996: Moderate 68 of 366 days1996: Unhealthy for Sensitive Groups 20 of 366 days1996: Unhealthy 5 of 366 days1997: Good 259 of 365 days1997: Moderate 75 of 365 days1997: Unhealthy for Sensitive Groups 22 of 365 days1997: Unhealthy 8 of 365 days1997: Very Unhealthy 1 of 365 days1998: Good 259 of 365 days1998: Moderate 67 of 365 days1998: Unhealthy for Sensitive Groups 31 of 365 days1998: Unhealthy 7 of 365 days1998: Very Unhealthy 1 of 365 days1999: Good 133 of 365 days1999: Moderate 200 of 365 days1999: Unhealthy for Sensitive Groups 29 of 365 days1999: Unhealthy 3 of 365 days2000: Good 90 of 366 days2000: Moderate 238 of 366 days2000: Unhealthy for Sensitive Groups 31 of 366 days2000: Unhealthy 7 of 366 days20002001: Good 102 of 365 days2001: Moderate 232 of 365 days2001: Unhealthy for Sensitive Groups 29 of 365 days2001: Unhealthy 2 of 365 days2002: Good 120 of 364 days2002: Moderate 204 of 364 days2002: Unhealthy for Sensitive Groups 30 of 364 days2002: Unhealthy 10 of 364 days2003: Good 197 of 365 days2003: Moderate 127 of 365 days2003: Unhealthy for Sensitive Groups 30 of 365 days2003: Unhealthy 11 of 365 days2004: Good 256 of 366 days2004: Moderate 104 of 366 days2004: Unhealthy for Sensitive Groups 6 of 366 days2005: Good 220 of 365 days2005: Moderate 107 of 365 days2005: Unhealthy for Sensitive Groups 28 of 365 days2005: Unhealthy 10 of 365 days20052006: Good 147 of 363 days2006: Moderate 183 of 363 days2006: Unhealthy for Sensitive Groups 23 of 363 days2006: Unhealthy 9 of 363 days2006: Very Unhealthy 1 of 363 days2007: Good 138 of 365 days2007: Moderate 202 of 365 days2007: Unhealthy for Sensitive Groups 20 of 365 days2007: Unhealthy 5 of 365 days2008: Good 165 of 366 days2008: Moderate 196 of 366 days2008: Unhealthy for Sensitive Groups 5 of 366 days2009: Good 172 of 365 days2009: Moderate 183 of 365 days2009: Unhealthy for Sensitive Groups 10 of 365 days2010: Good 174 of 365 days2010: Moderate 178 of 365 days2010: Unhealthy for Sensitive Groups 13 of 365 days20102011: Good 174 of 365 days2011: Moderate 169 of 365 days2011: Unhealthy for Sensitive Groups 19 of 365 days2011: Unhealthy 3 of 365 days2012: Good 163 of 364 days2012: Moderate 169 of 364 days2012: Unhealthy for Sensitive Groups 26 of 364 days2012: Unhealthy 6 of 364 days2013: Good 197 of 364 days2013: Moderate 160 of 364 days2013: Unhealthy for Sensitive Groups 7 of 364 days2014: Good 204 of 365 days2014: Moderate 157 of 365 days2014: Unhealthy for Sensitive Groups 4 of 365 days2015: Good 217 of 362 days2015: Moderate 141 of 362 days2015: Unhealthy for Sensitive Groups 4 of 362 days20152016: Good 273 of 361 days2016: Moderate 85 of 361 days2016: Unhealthy for Sensitive Groups 3 of 361 days2017: Good 248 of 364 days2017: Moderate 112 of 364 days2017: Unhealthy for Sensitive Groups 4 of 364 days2018: Good 251 of 363 days2018: Moderate 101 of 363 days2018: Unhealthy for Sensitive Groups 11 of 363 days2019: Good 266 of 365 days2019: Moderate 99 of 365 days2020: Good 287 of 364 days2020: Moderate 76 of 364 days2020: Unhealthy for Sensitive Groups 1 of 364 days20202021: Good 270 of 350 days2021: Moderate 76 of 350 days2021: Unhealthy for Sensitive Groups 4 of 350 days2022: Good 286 of 365 days2022: Moderate 75 of 365 days2022: Unhealthy for Sensitive Groups 4 of 365 days2023: Good 228 of 350 days2023: Moderate 105 of 350 days2023: Unhealthy for Sensitive Groups 16 of 350 days2023: Unhealthy 1 of 350 days2024: Good 286 of 366 days2024: Moderate 76 of 366 days2024: Unhealthy for Sensitive Groups 4 of 366 days2025: Good 270 of 363 days2025: Moderate 86 of 363 days2025: Unhealthy for Sensitive Groups 6 of 363 days2025: Unhealthy 1 of 363 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 year0501001501980: 90th percentile AQI 1261981: 90th percentile AQI 971982: 90th percentile AQI 841983: 90th percentile AQI 1041984: 90th percentile AQI 1121985: 90th percentile AQI 841986: 90th percentile AQI 741987: 90th percentile AQI 1011988: 90th percentile AQI 1191989: 90th percentile AQI 801990: 90th percentile AQI 741991: 90th percentile AQI 971992: 90th percentile AQI 801993: 90th percentile AQI 741994: 90th percentile AQI 1011995: 90th percentile AQI 1001996: 90th percentile AQI 901997: 90th percentile AQI 971998: 90th percentile AQI 1011999: 90th percentile AQI 972000: 90th percentile AQI 1012001: 90th percentile AQI 972002: 90th percentile AQI 1082003: 90th percentile AQI 1052004: 90th percentile AQI 712005: 90th percentile AQI 1052006: 90th percentile AQI 972007: 90th percentile AQI 902008: 90th percentile AQI 712009: 90th percentile AQI 702010: 90th percentile AQI 802011: 90th percentile AQI 842012: 90th percentile AQI 972013: 90th percentile AQI 742014: 90th percentile AQI 672015: 90th percentile AQI 642016: 90th percentile AQI 612017: 90th percentile AQI 672018: 90th percentile AQI 682019: 90th percentile AQI 612020: 90th percentile AQI 602021: 90th percentile AQI 642022: 90th percentile AQI 612023: 90th percentile AQI 802024: 90th percentile AQI 642025: 90th percentile AQI 641980: Median AQI 521981: Median AQI 471982: Median AQI 441983: Median AQI 431984: Median AQI 441985: Median AQI 411986: Median AQI 411987: Median AQI 451988: Median AQI 451989: Median AQI 431990: Median AQI 411991: Median AQI 441992: Median AQI 411993: Median AQI 401994: Median AQI 421995: Median AQI 421996: Median AQI 401997: Median AQI 411998: Median AQI 401999: Median AQI 562000: Median AQI 612001: Median AQI 592002: Median AQI 582003: Median AQI 462004: Median AQI 402005: Median AQI 452006: Median AQI 542007: Median AQI 552008: Median AQI 522009: Median AQI 512010: Median AQI 522011: Median AQI 522012: Median AQI 522013: Median AQI 492014: Median AQI 462015: Median AQI 462016: Median AQI 412017: Median AQI 432018: Median AQI 422019: Median AQI 432020: Median AQI 392021: Median AQI 412022: Median AQI 412023: Median AQI 432024: Median AQI 412025: Median AQI 421980198519901995200020052010201520202025
  • 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
Ozone21359%
Fine particles (PM2.5)15041%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
20253632708661004264156Ozone
20243662867640004164122Ozone
2023350228105161004380153Ozone
20223652867540004161112Ozone
20213502707640004164129Ozone
20203642877610003960101Ozone
2019365266990000436190Ozone
2018363251101110004268147Ozone
201736424811240004367129Ozone
20163612738530004161119Ozone
201536221714140004664115PM2.5
201436520415740004667120PM2.5
201336419716070004974136PM2.5
2012364163169266005297177PM2.5
2011365174169193005284172PM2.5
2010365174178130005280129PM2.5
2009365172183100005170143PM2.5
200836616519650005271122PM2.5
2007365138202205005590185PM2.5
2006363147183239105497201PM2.5
200536522010728100045105179Ozone
200436625610460004071122Ozone
200336519712730110046105190Ozone
200236412020430100058108192PM2.5
2001365102232292005997156PM2.5
2000366902383170061101195PM2.5
1999365133200293005697174PM2.5
1998365259673171040101204Ozone
199736525975228104197206Ozone
199636627368205004090190Ozone
19953652498019152042100221Ozone
1994365246783470042101195Ozone
199336528363163004074174Ozone
199236627178161004180179Ozone
199136524686258004497166Ozone
199036527080132004174172Ozone
198936525990151004380161Ozone
19883662228639163045119235Ozone
19873652211023570045101174Ozone
198636527774122004174195Ozone
198536526278176204184215Ozone
19843662259529143044112204Ozone
19833652398429121043104205Ozone
1982365239106182004484169Ozone
19813652131182310104797201Ozone
198036617514024216052126222Ozone

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 Missouri with a similar median AQI in 2025

All monitored counties in Missouri

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