EnviroNearby

Tehama County, California air quality history

Daily Air Quality Index summaries from EPA monitors in Tehama, California, 1986–2025.

78%
Good days in 2025
38
Median daily AQI, 2025
1
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 Tehama, California on 365 days. 284 of those days (78%) were in the Good range, and the median daily AQI was 38. 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 181 days. Across the years with fuller monitoring, the share of Good days rose: an average of 63% in 1990–1992 versus 71% in 2023–2025.

Years with fewer than 120 monitored days (1986, 1987, 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%1986: Good 8 of 10 days1986: Moderate 2 of 10 days19861987: Good 45 of 57 days1987: Moderate 11 of 57 days1987: Unhealthy for Sensitive Groups 1 of 57 days1988: Good 40 of 58 days1988: Moderate 18 of 58 days1989: Good 55 of 59 days1989: Moderate 4 of 59 days1990: Good 122 of 191 days1990: Moderate 32 of 191 days1990: Unhealthy for Sensitive Groups 26 of 191 days1990: Unhealthy 11 of 191 days1991: Good 139 of 246 days1991: Moderate 69 of 246 days1991: Unhealthy for Sensitive Groups 38 of 246 days19911992: Good 235 of 348 days1992: Moderate 74 of 348 days1992: Unhealthy for Sensitive Groups 32 of 348 days1992: Unhealthy 7 of 348 days1993: Good 286 of 355 days1993: Moderate 51 of 355 days1993: Unhealthy for Sensitive Groups 14 of 355 days1993: Unhealthy 4 of 355 days1994: Good 238 of 341 days1994: Moderate 78 of 341 days1994: Unhealthy for Sensitive Groups 24 of 341 days1994: Unhealthy 1 of 341 days1995: Good 207 of 313 days1995: Moderate 68 of 313 days1995: Unhealthy for Sensitive Groups 29 of 313 days1995: Unhealthy 9 of 313 days1996: Good 162 of 281 days1996: Moderate 77 of 281 days1996: Unhealthy for Sensitive Groups 42 of 281 days19961997: Good 252 of 354 days1997: Moderate 76 of 354 days1997: Unhealthy for Sensitive Groups 24 of 354 days1997: Unhealthy 2 of 354 days1998: Good 236 of 358 days1998: Moderate 61 of 358 days1998: Unhealthy for Sensitive Groups 51 of 358 days1998: Unhealthy 7 of 358 days1998: Very Unhealthy 3 of 358 days1999: Good 175 of 342 days1999: Moderate 95 of 342 days1999: Unhealthy for Sensitive Groups 53 of 342 days1999: Unhealthy 17 of 342 days1999: Very Unhealthy 2 of 342 days2000: Good 218 of 320 days2000: Moderate 70 of 320 days2000: Unhealthy for Sensitive Groups 30 of 320 days2000: Unhealthy 2 of 320 days2001: Good 168 of 279 days2001: Moderate 84 of 279 days2001: Unhealthy for Sensitive Groups 27 of 279 days20012002: Good 170 of 268 days2002: Moderate 59 of 268 days2002: Unhealthy for Sensitive Groups 32 of 268 days2002: Unhealthy 7 of 268 days2003: Good 155 of 278 days2003: Moderate 85 of 278 days2003: Unhealthy for Sensitive Groups 35 of 278 days2003: Unhealthy 3 of 278 days2004: Good 189 of 304 days2004: Moderate 67 of 304 days2004: Unhealthy for Sensitive Groups 47 of 304 days2004: Unhealthy 1 of 304 days2005: Good 188 of 295 days2005: Moderate 74 of 295 days2005: Unhealthy for Sensitive Groups 32 of 295 days2005: Unhealthy 1 of 295 days2006: Good 210 of 340 days2006: Moderate 83 of 340 days2006: Unhealthy for Sensitive Groups 40 of 340 days2006: Unhealthy 7 of 340 days20062007: Good 262 of 359 days2007: Moderate 68 of 359 days2007: Unhealthy for Sensitive Groups 28 of 359 days2007: Unhealthy 1 of 359 days2008: Good 196 of 314 days2008: Moderate 87 of 314 days2008: Unhealthy for Sensitive Groups 27 of 314 days2008: Unhealthy 4 of 314 days2009: Good 171 of 264 days2009: Moderate 62 of 264 days2009: Unhealthy for Sensitive Groups 31 of 264 days2010: Good 128 of 365 days2010: Moderate 219 of 365 days2010: Unhealthy for Sensitive Groups 18 of 365 days2011: Good 133 of 365 days2011: Moderate 217 of 365 days2011: Unhealthy for Sensitive Groups 15 of 365 days20112012: Good 183 of 366 days2012: Moderate 164 of 366 days2012: Unhealthy for Sensitive Groups 19 of 366 days2013: Good 233 of 365 days2013: Moderate 121 of 365 days2013: Unhealthy for Sensitive Groups 11 of 365 days2014: Good 227 of 364 days2014: Moderate 121 of 364 days2014: Unhealthy for Sensitive Groups 15 of 364 days2014: Unhealthy 1 of 364 days2015: Good 223 of 365 days2015: Moderate 123 of 365 days2015: Unhealthy for Sensitive Groups 18 of 365 days2015: Unhealthy 1 of 365 days2016: Good 218 of 366 days2016: Moderate 106 of 366 days2016: Unhealthy for Sensitive Groups 37 of 366 days2016: Unhealthy 5 of 366 days20162017: Good 237 of 365 days2017: Moderate 119 of 365 days2017: Unhealthy for Sensitive Groups 6 of 365 days2017: Unhealthy 3 of 365 days2018: Good 208 of 365 days2018: Moderate 128 of 365 days2018: Unhealthy for Sensitive Groups 16 of 365 days2018: Unhealthy 12 of 365 days2018: Very Unhealthy 1 of 365 days2019: Good 263 of 365 days2019: Moderate 102 of 365 days2020: Good 216 of 366 days2020: Moderate 117 of 366 days2020: Unhealthy for Sensitive Groups 12 of 366 days2020: Unhealthy 19 of 366 days2020: Very Unhealthy 2 of 366 days2021: Good 207 of 365 days2021: Moderate 122 of 365 days2021: Unhealthy for Sensitive Groups 21 of 365 days2021: Unhealthy 15 of 365 days20212022: Good 245 of 365 days2022: Moderate 117 of 365 days2022: Unhealthy for Sensitive Groups 3 of 365 days2023: Good 242 of 365 days2023: Moderate 117 of 365 days2023: Unhealthy for Sensitive Groups 6 of 365 days2024: Good 252 of 366 days2024: Moderate 112 of 366 days2024: Unhealthy for Sensitive Groups 2 of 366 days2025: Good 284 of 365 days2025: Moderate 80 of 365 days2025: Unhealthy for Sensitive Groups 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 year0501001501986: 90th percentile AQI 691987: 90th percentile AQI 601988: 90th percentile AQI 621989: 90th percentile AQI 481990: 90th percentile AQI 1331991: 90th percentile AQI 1151992: 90th percentile AQI 1081993: 90th percentile AQI 841994: 90th percentile AQI 931995: 90th percentile AQI 1051996: 90th percentile AQI 1191997: 90th percentile AQI 901998: 90th percentile AQI 1191999: 90th percentile AQI 1292000: 90th percentile AQI 1012001: 90th percentile AQI 1002002: 90th percentile AQI 1122003: 90th percentile AQI 1052004: 90th percentile AQI 1082005: 90th percentile AQI 1012006: 90th percentile AQI 1192007: 90th percentile AQI 972008: 90th percentile AQI 1002009: 90th percentile AQI 1052010: 90th percentile AQI 902011: 90th percentile AQI 842012: 90th percentile AQI 932013: 90th percentile AQI 762014: 90th percentile AQI 802015: 90th percentile AQI 872016: 90th percentile AQI 1082017: 90th percentile AQI 772018: 90th percentile AQI 962019: 90th percentile AQI 642020: 90th percentile AQI 942021: 90th percentile AQI 1002022: 90th percentile AQI 742023: 90th percentile AQI 672024: 90th percentile AQI 712025: 90th percentile AQI 541986: Median AQI 391987: Median AQI 311988: Median AQI 351989: Median AQI 291990: Median AQI 421991: Median AQI 471992: Median AQI 431993: Median AQI 371994: Median AQI 381995: Median AQI 411996: Median AQI 461997: Median AQI 391998: Median AQI 441999: Median AQI 502000: Median AQI 402001: Median AQI 442002: Median AQI 442003: Median AQI 462004: Median AQI 422005: Median AQI 432006: Median AQI 412007: Median AQI 392008: Median AQI 472009: Median AQI 432010: Median AQI 552011: Median AQI 552012: Median AQI 512013: Median AQI 442014: Median AQI 452015: Median AQI 472016: Median AQI 452017: Median AQI 422018: Median AQI 482019: Median AQI 432020: Median AQI 462021: Median AQI 472022: Median AQI 442023: Median AQI 442024: Median AQI 432025: Median AQI 38198619911996200120062011201620212025
  • 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
Ozone18150%
Fine particles (PM2.5)17849%
Coarse particles (PM10)62%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
20253652848010003854108Ozone
202436625211220004371109Ozone
202336524211760004467136Ozone
202236524511730004474108Ozone
202136520712221150047100193Ozone
20203662161171219204694218Ozone
20193652631020000436493Ozone
20183652081281612104896206Ozone
201736523711963004277172Ozone
20163662181063750045108174Ozone
2015365223123181004787154Ozone
2014364227121151004580151Ozone
2013365233121110004476136Ozone
2012366183164190005193150Ozone
2011365133217150005584122PM2.5
2010365128219180005590136PM2.5
2009264171623100043105136Ozone
2008314196872740047100197Ozone
200735926268281003997154Ozone
2006340210834070041119166Ozone
2005295188743210043101151Ozone
2004304189674710042108159Ozone
2003278155853530046105156Ozone
2002268170593270044112174Ozone
2001279168842700044100150Ozone
2000320218703020040101156Ozone
19993421759553172050129203Ozone
1998358236615173044119207Ozone
199735425276242003990169Ozone
1996281162774200046119147Ozone
1995313207682990041105195Ozone
199434123878241003893154Ozone
199335528651144003784169Ozone
1992348235743270043108164Ozone
1991246139693800047115150Ozone
19901911223226110042133187Ozone
1989595540000294857PM10
19885840180000356273PM10
198757451110003160102PM10
198610820000396969PM10

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 1986–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem