EnviroNearby

Tuolumne County, California air quality history

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

87%
Good days in 2025
39
Median daily AQI, 2025
1
Days above 100 in 2025
338
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Tuolumne, California on 338 days. 294 of those days (87%) were in the Good range, and the median daily AQI was 39. 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 338 days. Across the years with fuller monitoring, the share of Good days rose: an average of 32% in 1980–1988 versus 83% 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 80 of 356 days1980: Moderate 213 of 356 days1980: Unhealthy for Sensitive Groups 50 of 356 days1980: Unhealthy 12 of 356 days1980: Very Unhealthy 1 of 356 days19801981: Good 23 of 299 days1981: Moderate 232 of 299 days1981: Unhealthy for Sensitive Groups 39 of 299 days1981: Unhealthy 4 of 299 days1981: Very Unhealthy 1 of 299 days1988: Good 163 of 251 days1988: Moderate 59 of 251 days1988: Unhealthy for Sensitive Groups 27 of 251 days1988: Unhealthy 2 of 251 days1989: Good 255 of 307 days1989: Moderate 45 of 307 days1989: Unhealthy for Sensitive Groups 7 of 307 days1990: Good 164 of 211 days1990: Moderate 39 of 211 days1990: Unhealthy for Sensitive Groups 8 of 211 days1991: Good 108 of 210 days1991: Moderate 88 of 210 days1991: Unhealthy for Sensitive Groups 14 of 210 days19911992: Good 251 of 355 days1992: Moderate 74 of 355 days1992: Unhealthy for Sensitive Groups 29 of 355 days1992: Unhealthy 1 of 355 days1993: Good 225 of 365 days1993: Moderate 94 of 365 days1993: Unhealthy for Sensitive Groups 40 of 365 days1993: Unhealthy 6 of 365 days1994: Good 211 of 365 days1994: Moderate 86 of 365 days1994: Unhealthy for Sensitive Groups 61 of 365 days1994: Unhealthy 7 of 365 days1995: Good 225 of 364 days1995: Moderate 86 of 364 days1995: Unhealthy for Sensitive Groups 41 of 364 days1995: Unhealthy 12 of 364 days1996: Good 211 of 366 days1996: Moderate 75 of 366 days1996: Unhealthy for Sensitive Groups 61 of 366 days1996: Unhealthy 18 of 366 days1996: Very Unhealthy 1 of 366 days19961997: Good 194 of 365 days1997: Moderate 117 of 365 days1997: Unhealthy for Sensitive Groups 49 of 365 days1997: Unhealthy 4 of 365 days1997: Very Unhealthy 1 of 365 days1998: Good 208 of 365 days1998: Moderate 76 of 365 days1998: Unhealthy for Sensitive Groups 58 of 365 days1998: Unhealthy 22 of 365 days1998: Very Unhealthy 1 of 365 days1999: Good 176 of 365 days1999: Moderate 88 of 365 days1999: Unhealthy for Sensitive Groups 77 of 365 days1999: Unhealthy 24 of 365 days2000: Good 184 of 363 days2000: Moderate 98 of 363 days2000: Unhealthy for Sensitive Groups 61 of 363 days2000: Unhealthy 20 of 363 days2001: Good 208 of 365 days2001: Moderate 108 of 365 days2001: Unhealthy for Sensitive Groups 46 of 365 days2001: Unhealthy 3 of 365 days20012002: Good 195 of 365 days2002: Moderate 74 of 365 days2002: Unhealthy for Sensitive Groups 76 of 365 days2002: Unhealthy 20 of 365 days2003: Good 208 of 365 days2003: Moderate 100 of 365 days2003: Unhealthy for Sensitive Groups 52 of 365 days2003: Unhealthy 5 of 365 days2004: Good 227 of 366 days2004: Moderate 123 of 366 days2004: Unhealthy for Sensitive Groups 16 of 366 days2005: Good 264 of 365 days2005: Moderate 81 of 365 days2005: Unhealthy for Sensitive Groups 19 of 365 days2005: Unhealthy 1 of 365 days2006: Good 268 of 365 days2006: Moderate 81 of 365 days2006: Unhealthy for Sensitive Groups 16 of 365 days20062007: Good 246 of 364 days2007: Moderate 79 of 364 days2007: Unhealthy for Sensitive Groups 37 of 364 days2007: Unhealthy 2 of 364 days2008: Good 237 of 365 days2008: Moderate 90 of 365 days2008: Unhealthy for Sensitive Groups 29 of 365 days2008: Unhealthy 7 of 365 days2008: Very Unhealthy 2 of 365 days2009: Good 256 of 361 days2009: Moderate 86 of 361 days2009: Unhealthy for Sensitive Groups 19 of 361 days2010: Good 274 of 365 days2010: Moderate 83 of 365 days2010: Unhealthy for Sensitive Groups 8 of 365 days2011: Good 259 of 355 days2011: Moderate 84 of 355 days2011: Unhealthy for Sensitive Groups 12 of 355 days20112012: Good 246 of 364 days2012: Moderate 105 of 364 days2012: Unhealthy for Sensitive Groups 13 of 364 days2013: Good 284 of 364 days2013: Moderate 78 of 364 days2013: Unhealthy for Sensitive Groups 2 of 364 days2014: Good 214 of 334 days2014: Moderate 104 of 334 days2014: Unhealthy for Sensitive Groups 16 of 334 days2015: Good 264 of 364 days2015: Moderate 89 of 364 days2015: Unhealthy for Sensitive Groups 11 of 364 days2016: Good 223 of 354 days2016: Moderate 86 of 354 days2016: Unhealthy for Sensitive Groups 38 of 354 days2016: Unhealthy 7 of 354 days20162017: Good 231 of 362 days2017: Moderate 106 of 362 days2017: Unhealthy for Sensitive Groups 25 of 362 days2018: Good 254 of 348 days2018: Moderate 73 of 348 days2018: Unhealthy for Sensitive Groups 20 of 348 days2018: Unhealthy 1 of 348 days2019: Good 273 of 358 days2019: Moderate 83 of 358 days2019: Unhealthy for Sensitive Groups 2 of 358 days2020: Good 277 of 353 days2020: Moderate 71 of 353 days2020: Unhealthy for Sensitive Groups 5 of 353 days2021: Good 295 of 360 days2021: Moderate 63 of 360 days2021: Unhealthy for Sensitive Groups 2 of 360 days20212022: Good 237 of 250 days2022: Moderate 12 of 250 days2022: Unhealthy for Sensitive Groups 1 of 250 days2023: Good 237 of 290 days2023: Moderate 51 of 290 days2023: Unhealthy for Sensitive Groups 2 of 290 days2024: Good 286 of 354 days2024: Moderate 64 of 354 days2024: Unhealthy for Sensitive Groups 4 of 354 days2025: Good 294 of 338 days2025: Moderate 43 of 338 days2025: Unhealthy for Sensitive Groups 1 of 338 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 1231981: 90th percentile AQI 1151988: 90th percentile AQI 1011989: 90th percentile AQI 671990: 90th percentile AQI 771991: 90th percentile AQI 931992: 90th percentile AQI 931993: 90th percentile AQI 1051994: 90th percentile AQI 1151995: 90th percentile AQI 1151996: 90th percentile AQI 1361997: 90th percentile AQI 1121998: 90th percentile AQI 1431999: 90th percentile AQI 1402000: 90th percentile AQI 1332001: 90th percentile AQI 1122002: 90th percentile AQI 1332003: 90th percentile AQI 1152004: 90th percentile AQI 872005: 90th percentile AQI 872006: 90th percentile AQI 842007: 90th percentile AQI 1012008: 90th percentile AQI 1012009: 90th percentile AQI 902010: 90th percentile AQI 802011: 90th percentile AQI 842012: 90th percentile AQI 872013: 90th percentile AQI 642014: 90th percentile AQI 872015: 90th percentile AQI 772016: 90th percentile AQI 1082017: 90th percentile AQI 932018: 90th percentile AQI 802019: 90th percentile AQI 672020: 90th percentile AQI 642021: 90th percentile AQI 612022: 90th percentile AQI 482023: 90th percentile AQI 612024: 90th percentile AQI 672025: 90th percentile AQI 541980: Median AQI 701981: Median AQI 711988: Median AQI 411989: Median AQI 321990: Median AQI 391991: Median AQI 491992: Median AQI 391993: Median AQI 431994: Median AQI 451995: Median AQI 441996: Median AQI 461997: Median AQI 491998: Median AQI 461999: Median AQI 582000: Median AQI 492001: Median AQI 452002: Median AQI 472003: Median AQI 442004: Median AQI 442005: Median AQI 412006: Median AQI 382007: Median AQI 422008: Median AQI 452009: Median AQI 422010: Median AQI 412011: Median AQI 412012: Median AQI 422013: Median AQI 432014: Median AQI 462015: Median AQI 432016: Median AQI 442017: Median AQI 442018: Median AQI 432019: Median AQI 432020: Median AQI 412021: Median AQI 412022: Median AQI 392023: Median AQI 432024: Median AQI 402025: Median AQI 39198019911996200120062011201620212025
  • 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
Ozone338100%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
20253382944310003954105Ozone
20243542866440004067115Ozone
20232902375120004361112Ozone
20222502371210003948108Ozone
20213602956320004161136Ozone
20203532777150004164143Ozone
20193582738320004367108Ozone
201834825473201004380154Ozone
2017362231106250004493143Ozone
2016354223863870044108164Ozone
201536426489110004377126Ozone
2014334214104160004687133Ozone
20133642847820004364119Ozone
2012364246105130004287136Ozone
201135525984120004184126Ozone
20103652748380004180147Ozone
200936125686190004290129Ozone
2008365237902972045101209Ozone
2007364246793720042101169Ozone
200636526881160003884143Ozone
200536526481191004187159Ozone
2004366227123160004487140Ozone
20033652081005250044115156Ozone
20023651957476200047133190Ozone
20013652081084630045112179Ozone
20003631849861200049133197Ozone
19993651768877240058140195Ozone
19983652087658221046143202Ozone
19973651941174941049112202Ozone
19963662117561181046136203Ozone
19953642258641120044115200Ozone
1994365211866170045115172Ozone
1993365225944060043105156Ozone
199235525174291003993179Ozone
199121010888140004993129Ozone
19902111643980003977136Ozone
19893072554570003267126Ozone
1988251163592720041101151Ozone
1981299232323941071115204CO
19803568021350121070123208CO

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