EnviroNearby

Glenn County, California air quality history

Daily Air Quality Index summaries from EPA monitors in Glenn, California, 1980–2025.

80%
Good days in 2025
40
Median daily AQI, 2025
0
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 Glenn, California on 365 days. 292 of those days (80%) were in the Good range, and the median daily AQI was 40. That median is lower than the typical monitored county in California (median 45.5 across 46 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 68% in 1980–1982 versus 78% in 2023–2025.

Years with fewer than 120 monitored days (1988, 1989) 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 261 of 358 days1980: Moderate 66 of 358 days1980: Unhealthy for Sensitive Groups 30 of 358 days1980: Unhealthy 1 of 358 days19801981: Good 242 of 318 days1981: Moderate 67 of 318 days1981: Unhealthy for Sensitive Groups 9 of 318 days1982: Good 83 of 148 days1982: Moderate 48 of 148 days1982: Unhealthy for Sensitive Groups 17 of 148 days1983: Good 100 of 171 days1983: Moderate 52 of 171 days1983: Unhealthy for Sensitive Groups 16 of 171 days1983: Unhealthy 3 of 171 days1984: Good 84 of 153 days1984: Moderate 55 of 153 days1984: Unhealthy for Sensitive Groups 13 of 153 days1984: Unhealthy 1 of 153 days1985: Good 109 of 176 days1985: Moderate 46 of 176 days1985: Unhealthy for Sensitive Groups 19 of 176 days1985: Unhealthy 2 of 176 days19851986: Good 106 of 191 days1986: Moderate 57 of 191 days1986: Unhealthy for Sensitive Groups 28 of 191 days1987: Good 83 of 213 days1987: Moderate 90 of 213 days1987: Unhealthy for Sensitive Groups 33 of 213 days1987: Unhealthy 7 of 213 days1988: Good 48 of 59 days1988: Moderate 11 of 59 days1989: Good 58 of 60 days1989: Moderate 2 of 60 days1990: Good 147 of 195 days1990: Moderate 27 of 195 days1990: Unhealthy for Sensitive Groups 20 of 195 days1990: Unhealthy 1 of 195 days19901991: Good 263 of 349 days1991: Moderate 77 of 349 days1991: Unhealthy for Sensitive Groups 9 of 349 days1992: Good 171 of 290 days1992: Moderate 77 of 290 days1992: Unhealthy for Sensitive Groups 38 of 290 days1992: Unhealthy 4 of 290 days1993: Good 301 of 365 days1993: Moderate 47 of 365 days1993: Unhealthy for Sensitive Groups 17 of 365 days1994: Good 240 of 363 days1994: Moderate 94 of 363 days1994: Unhealthy for Sensitive Groups 27 of 363 days1994: Unhealthy 2 of 363 days1995: Good 245 of 365 days1995: Moderate 93 of 365 days1995: Unhealthy for Sensitive Groups 26 of 365 days1995: Unhealthy 1 of 365 days19951996: Good 253 of 360 days1996: Moderate 90 of 360 days1996: Unhealthy for Sensitive Groups 17 of 360 days1997: Good 287 of 365 days1997: Moderate 67 of 365 days1997: Unhealthy for Sensitive Groups 11 of 365 days1998: Good 269 of 365 days1998: Moderate 86 of 365 days1998: Unhealthy for Sensitive Groups 9 of 365 days1998: Unhealthy 1 of 365 days1999: Good 241 of 365 days1999: Moderate 99 of 365 days1999: Unhealthy for Sensitive Groups 24 of 365 days1999: Unhealthy 1 of 365 days2000: Good 284 of 366 days2000: Moderate 76 of 366 days2000: Unhealthy for Sensitive Groups 6 of 366 days20002001: Good 259 of 364 days2001: Moderate 89 of 364 days2001: Unhealthy for Sensitive Groups 16 of 364 days2002: Good 253 of 365 days2002: Moderate 105 of 365 days2002: Unhealthy for Sensitive Groups 7 of 365 days2003: Good 278 of 365 days2003: Moderate 80 of 365 days2003: Unhealthy for Sensitive Groups 7 of 365 days2004: Good 309 of 363 days2004: Moderate 54 of 363 days2005: Good 323 of 364 days2005: Moderate 41 of 364 days20052006: Good 259 of 364 days2006: Moderate 97 of 364 days2006: Unhealthy for Sensitive Groups 7 of 364 days2006: Unhealthy 1 of 364 days2007: Good 196 of 365 days2007: Moderate 157 of 365 days2007: Unhealthy for Sensitive Groups 12 of 365 days2008: Good 168 of 365 days2008: Moderate 176 of 365 days2008: Unhealthy for Sensitive Groups 9 of 365 days2008: Unhealthy 9 of 365 days2008: Very Unhealthy 3 of 365 days2009: Good 204 of 365 days2009: Moderate 157 of 365 days2009: Unhealthy for Sensitive Groups 4 of 365 days2010: Good 229 of 365 days2010: Moderate 136 of 365 days20102011: Good 198 of 365 days2011: Moderate 165 of 365 days2011: Unhealthy for Sensitive Groups 2 of 365 days2012: Good 223 of 366 days2012: Moderate 142 of 366 days2012: Unhealthy for Sensitive Groups 1 of 366 days2013: Good 181 of 361 days2013: Moderate 179 of 361 days2013: Unhealthy for Sensitive Groups 1 of 361 days2014: Good 244 of 365 days2014: Moderate 120 of 365 days2014: Unhealthy for Sensitive Groups 1 of 365 days2015: Good 221 of 365 days2015: Moderate 144 of 365 days20152016: Good 194 of 362 days2016: Moderate 168 of 362 days2017: Good 231 of 365 days2017: Moderate 127 of 365 days2017: Unhealthy for Sensitive Groups 7 of 365 days2018: Good 242 of 363 days2018: Moderate 105 of 363 days2018: Unhealthy for Sensitive Groups 9 of 363 days2018: Unhealthy 6 of 363 days2018: Very Unhealthy 1 of 363 days2019: Good 274 of 362 days2019: Moderate 88 of 362 days2020: Good 200 of 364 days2020: Moderate 135 of 364 days2020: Unhealthy for Sensitive Groups 7 of 364 days2020: Unhealthy 19 of 364 days2020: Very Unhealthy 3 of 364 days20202021: Good 244 of 365 days2021: Moderate 106 of 365 days2021: Unhealthy for Sensitive Groups 9 of 365 days2021: Unhealthy 6 of 365 days2022: Good 264 of 360 days2022: Moderate 95 of 360 days2022: Unhealthy for Sensitive Groups 1 of 360 days2023: Good 273 of 363 days2023: Moderate 90 of 363 days2024: Good 292 of 366 days2024: Moderate 74 of 366 days2025: Good 292 of 365 days2025: Moderate 73 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 year0501001501980: 90th percentile AQI 1001981: 90th percentile AQI 841982: 90th percentile AQI 1011983: 90th percentile AQI 1011984: 90th percentile AQI 1001985: 90th percentile AQI 1081986: 90th percentile AQI 1081987: 90th percentile AQI 1151988: 90th percentile AQI 591989: 90th percentile AQI 431990: 90th percentile AQI 1011991: 90th percentile AQI 741992: 90th percentile AQI 1151993: 90th percentile AQI 711994: 90th percentile AQI 971995: 90th percentile AQI 971996: 90th percentile AQI 901997: 90th percentile AQI 671998: 90th percentile AQI 801999: 90th percentile AQI 932000: 90th percentile AQI 672001: 90th percentile AQI 802002: 90th percentile AQI 772003: 90th percentile AQI 672004: 90th percentile AQI 612005: 90th percentile AQI 512006: 90th percentile AQI 702007: 90th percentile AQI 782008: 90th percentile AQI 802009: 90th percentile AQI 692010: 90th percentile AQI 622011: 90th percentile AQI 642012: 90th percentile AQI 702013: 90th percentile AQI 672014: 90th percentile AQI 612015: 90th percentile AQI 682016: 90th percentile AQI 642017: 90th percentile AQI 632018: 90th percentile AQI 712019: 90th percentile AQI 582020: 90th percentile AQI 842021: 90th percentile AQI 652022: 90th percentile AQI 612023: 90th percentile AQI 582024: 90th percentile AQI 542025: 90th percentile AQI 541980: Median AQI 371981: Median AQI 321982: Median AQI 471983: Median AQI 441984: Median AQI 481985: Median AQI 461986: Median AQI 491987: Median AQI 601988: Median AQI 301989: Median AQI 231990: Median AQI 331991: Median AQI 371992: Median AQI 441993: Median AQI 371994: Median AQI 401995: Median AQI 441996: Median AQI 401997: Median AQI 381998: Median AQI 411999: Median AQI 442000: Median AQI 402001: Median AQI 432002: Median AQI 432003: Median AQI 402004: Median AQI 372005: Median AQI 372006: Median AQI 422007: Median AQI 492008: Median AQI 522009: Median AQI 462010: Median AQI 442011: Median AQI 492012: Median AQI 462013: Median AQI 502014: Median AQI 442015: Median AQI 462016: Median AQI 482017: Median AQI 462018: Median AQI 392019: Median AQI 422020: Median AQI 462021: Median AQI 422022: Median AQI 422023: Median AQI 412024: Median AQI 392025: Median AQI 401980198519901995200020052010201520202025
  • 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
Ozone22461%
Fine particles (PM2.5)11732%
Coarse particles (PM10)247%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
2025365292730000405494Ozone
2024366292740000395480Ozone
2023363273900000415897Ozone
20223602649510004261104Ozone
202136524410696004265192Ozone
2020364200135719304684221PM2.5
2019362274880000425886Ozone
201836324210596103971255PM2.5
201736523112770004663150PM2.5
20163621941680000486492PM2.5
20153652211440000466893Ozone
201436524412010004461105Ozone
201336118117910005067101PM2.5
201236622314210004670106Ozone
201136519816520004964105PM2.5
20103652291360000446292PM2.5
200936520415740004669115PM2.5
200836516817699305280261PM2.5
2007365196157120004978138PM2.5
20063642599771004270153Ozone
20053643234100003751100Ozone
20043633095400003761100Ozone
20033652788070004067129Ozone
200236525310570004377122Ozone
200136425989160004380147Ozone
20003662847660004067126Ozone
199936524199241004493169Ozone
19983652698691004180156Ozone
199736528767110003867133Ozone
199636025390170004090136Ozone
199536524593261004497154Ozone
199436324094272004097151Ozone
199336530147170003771143Ozone
1992290171773840044115156Ozone
19913492637790003774140Ozone
1990195147272010033101151Ozone
1989605820000234360PM10
19885948110000305970PM10
198721383903370060115179Ozone
1986191106572800049108143Ozone
1985176109461920046108161Ozone
198415384551310048100156Ozone
1983171100521630044101174Ozone
198214883481700047101133Ozone
19813182426790003284143Ozone
1980358261663010037100156Ozone

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 California with a similar median AQI in 2025

All monitored counties in California

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