EnviroNearby

Kay County, Oklahoma air quality history

Daily Air Quality Index summaries from EPA monitors in Kay, Oklahoma, 1988–2025.

71%
Good days in 2025
37
Median daily AQI, 2025
2
Days above 100 in 2025
361
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Kay, Oklahoma on 361 days. 257 of those days (71%) were in the Good range, and the median daily AQI was 37. That median is lower than the typical monitored county in Oklahoma (median 44 across 19 counties), and lower than the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 361 days. Across the years with fuller monitoring, the share of Good days fell: an average of 77% in 1989–2000 versus 62% in 2023–2025.

Years with fewer than 120 monitored days (1993, 1994, 1995, 1996, 1997, 1998…) 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%1988: Good 47 of 49 days1988: Moderate 2 of 49 days19881989: Good 350 of 358 days1989: Moderate 8 of 358 days1990: Good 103 of 108 days1990: Moderate 5 of 108 days1991: Good 44 of 46 days1991: Moderate 2 of 46 days1992: Good 45 of 47 days1992: Moderate 2 of 47 days1993: Good 51 of 53 days1993: Moderate 2 of 53 days19931994: Good 53 of 55 days1994: Moderate 2 of 55 days1995: Good 52 of 53 days1995: Moderate 1 of 53 days1996: Good 51 of 54 days1996: Moderate 3 of 54 days1997: Good 52 of 53 days1997: Moderate 1 of 53 days1998: Good 9 of 9 days19981999: Good 142 of 190 days1999: Moderate 34 of 190 days1999: Unhealthy for Sensitive Groups 10 of 190 days1999: Unhealthy 4 of 190 days2000: Good 219 of 366 days2000: Moderate 117 of 366 days2000: Unhealthy for Sensitive Groups 27 of 366 days2000: Unhealthy 3 of 366 days2001: Good 214 of 365 days2001: Moderate 127 of 365 days2001: Unhealthy for Sensitive Groups 23 of 365 days2001: Unhealthy 1 of 365 days2002: Good 240 of 365 days2002: Moderate 116 of 365 days2002: Unhealthy for Sensitive Groups 9 of 365 days2003: Good 198 of 365 days2003: Moderate 149 of 365 days2003: Unhealthy for Sensitive Groups 18 of 365 days20032004: Good 238 of 366 days2004: Moderate 113 of 366 days2004: Unhealthy for Sensitive Groups 15 of 366 days2005: Good 218 of 365 days2005: Moderate 124 of 365 days2005: Unhealthy for Sensitive Groups 23 of 365 days2006: Good 220 of 365 days2006: Moderate 113 of 365 days2006: Unhealthy for Sensitive Groups 29 of 365 days2006: Unhealthy 3 of 365 days2007: Good 263 of 363 days2007: Moderate 97 of 363 days2007: Unhealthy for Sensitive Groups 3 of 363 days2008: Good 258 of 359 days2008: Moderate 98 of 359 days2008: Unhealthy for Sensitive Groups 2 of 359 days2008: Unhealthy 1 of 359 days20082009: Good 100 of 363 days2009: Moderate 259 of 363 days2009: Unhealthy for Sensitive Groups 3 of 363 days2009: Unhealthy 1 of 363 days2010: Good 173 of 364 days2010: Moderate 191 of 364 days2011: Good 175 of 285 days2011: Moderate 87 of 285 days2011: Unhealthy for Sensitive Groups 23 of 285 days2012: Good 111 of 312 days2012: Moderate 182 of 312 days2012: Unhealthy for Sensitive Groups 18 of 312 days2012: Unhealthy 1 of 312 days2013: Good 156 of 365 days2013: Moderate 205 of 365 days2013: Unhealthy for Sensitive Groups 4 of 365 days20132014: Good 112 of 365 days2014: Moderate 250 of 365 days2014: Unhealthy for Sensitive Groups 3 of 365 days2015: Good 139 of 362 days2015: Moderate 222 of 362 days2015: Unhealthy for Sensitive Groups 1 of 362 days2016: Good 165 of 361 days2016: Moderate 193 of 361 days2016: Unhealthy for Sensitive Groups 3 of 361 days2017: Good 151 of 365 days2017: Moderate 214 of 365 days2018: Good 181 of 365 days2018: Moderate 182 of 365 days2018: Unhealthy for Sensitive Groups 2 of 365 days20182019: Good 206 of 365 days2019: Moderate 158 of 365 days2019: Unhealthy for Sensitive Groups 1 of 365 days2020: Good 171 of 366 days2020: Moderate 193 of 366 days2020: Unhealthy for Sensitive Groups 2 of 366 days2021: Good 167 of 354 days2021: Moderate 178 of 354 days2021: Unhealthy for Sensitive Groups 8 of 354 days2021: Unhealthy 1 of 354 days2022: Good 225 of 361 days2022: Moderate 136 of 361 days2023: Good 172 of 335 days2023: Moderate 162 of 335 days2023: Unhealthy for Sensitive Groups 1 of 335 days20232024: Good 223 of 356 days2024: Moderate 128 of 356 days2024: Unhealthy for Sensitive Groups 4 of 356 days2024: Unhealthy 1 of 356 days2025: Good 257 of 361 days2025: Moderate 102 of 361 days2025: Unhealthy for Sensitive Groups 2 of 361 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 year0501001988: 90th percentile AQI 391989: 90th percentile AQI 421990: 90th percentile AQI 441991: 90th percentile AQI 381992: 90th percentile AQI 421993: 90th percentile AQI 431994: 90th percentile AQI 381995: 90th percentile AQI 381996: 90th percentile AQI 451997: 90th percentile AQI 321998: 90th percentile AQI 461999: 90th percentile AQI 972000: 90th percentile AQI 952001: 90th percentile AQI 932002: 90th percentile AQI 772003: 90th percentile AQI 902004: 90th percentile AQI 772005: 90th percentile AQI 932006: 90th percentile AQI 972007: 90th percentile AQI 672008: 90th percentile AQI 652009: 90th percentile AQI 742010: 90th percentile AQI 632011: 90th percentile AQI 972012: 90th percentile AQI 912013: 90th percentile AQI 712014: 90th percentile AQI 712015: 90th percentile AQI 622016: 90th percentile AQI 632017: 90th percentile AQI 652018: 90th percentile AQI 642019: 90th percentile AQI 612020: 90th percentile AQI 622021: 90th percentile AQI 722022: 90th percentile AQI 592023: 90th percentile AQI 632024: 90th percentile AQI 612025: 90th percentile AQI 571988: Median AQI 271989: Median AQI 251990: Median AQI 281991: Median AQI 251992: Median AQI 251993: Median AQI 241994: Median AQI 231995: Median AQI 191996: Median AQI 201997: Median AQI 201998: Median AQI 291999: Median AQI 282000: Median AQI 442001: Median AQI 462002: Median AQI 432003: Median AQI 482004: Median AQI 442005: Median AQI 462006: Median AQI 462007: Median AQI 412008: Median AQI 402009: Median AQI 572010: Median AQI 512011: Median AQI 462012: Median AQI 552013: Median AQI 532014: Median AQI 562015: Median AQI 532016: Median AQI 522017: Median AQI 532018: Median AQI 512019: Median AQI 472020: Median AQI 512021: Median AQI 522022: Median AQI 432023: Median AQI 492024: Median AQI 422025: Median AQI 37198819931998200320082013201820232025
  • 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)361100%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
202536125710220003757141PM2.5
202435622312841004261193PM2.5
202333517216210004963122PM2.5
20223612251360000435993PM2.5
202135416717881005272168PM2.5
202036617119320005162113PM2.5
201936520615810004761106PM2.5
201836518118220005164114PM2.5
20173651512140000536590PM2.5
201636116519330005263126PM2.5
201536213922210005362107PM2.5
201436511225030005671122PM2.5
201336515620540005371115PM2.5
2012312111182181005591159PM2.5
201128517587230004697143Ozone
20103641731910000516393PM2.5
200936310025931005774161PM2.5
20083592589821004065159Ozone
20073632639730004167133Ozone
2006365220113293004697166Ozone
2005365218124230004693150Ozone
2004366238113150004477147Ozone
2003365198149180004890140Ozone
200236524011690004377119Ozone
2001365214127231004693164Ozone
2000366219117273004495161Ozone
199919014234104002897187PM10
19989900000294646PM10
1997535210000203258PM10
1996545130000204567PM10
1995535210000193853PM10
1994555320000233869PM10
1993535120000244355PM10
1992474520000254254PM10
1991464420000253858PM10
199010810350000284466NO2
198935835080000254260NO2
1988494720000273994NO2

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 Oklahoma with a similar median AQI in 2025

All monitored counties in Oklahoma

Source: U.S. EPA AirData, “Annual AQI by County” files for 1988–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem