EnviroNearby

Lake County, California air quality history

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

99%
Good days in 2025
31
Median daily AQI, 2025
0
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 Lake, California on 363 days. 360 of those days (99%) were in the Good range, and the median daily AQI was 31. That median is lower than the typical monitored county in California (median 45.5 across 46 counties), and lower than the typical monitored U.S. county (40). The main pollutant was ozone on 352 days. Across the years with fuller monitoring, the share of Good days rose: an average of 92% in 1980–1982 versus 99% 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 203 of 238 days1980: Moderate 32 of 238 days1980: Unhealthy for Sensitive Groups 3 of 238 days19801981: Good 347 of 354 days1981: Moderate 7 of 354 days1982: Good 311 of 336 days1982: Moderate 23 of 336 days1982: Unhealthy for Sensitive Groups 2 of 336 days1983: Good 318 of 322 days1983: Moderate 4 of 322 days1984: Good 334 of 359 days1984: Moderate 24 of 359 days1984: Unhealthy for Sensitive Groups 1 of 359 days1985: Good 348 of 360 days1985: Moderate 12 of 360 days19851986: Good 318 of 344 days1986: Moderate 22 of 344 days1986: Unhealthy for Sensitive Groups 4 of 344 days1987: Good 320 of 357 days1987: Moderate 34 of 357 days1987: Unhealthy for Sensitive Groups 3 of 357 days1988: Good 356 of 363 days1988: Moderate 7 of 363 days1989: Good 355 of 355 days1990: Good 361 of 365 days1990: Moderate 4 of 365 days19901991: Good 341 of 361 days1991: Moderate 20 of 361 days1992: Good 284 of 286 days1992: Moderate 2 of 286 days1993: Good 351 of 359 days1993: Moderate 7 of 359 days1993: Unhealthy for Sensitive Groups 1 of 359 days1994: Good 308 of 364 days1994: Moderate 54 of 364 days1994: Unhealthy for Sensitive Groups 2 of 364 days1995: Good 357 of 362 days1995: Moderate 5 of 362 days19951996: Good 352 of 361 days1996: Moderate 9 of 361 days1997: Good 302 of 309 days1997: Moderate 7 of 309 days1998: Good 357 of 362 days1998: Moderate 4 of 362 days1998: Unhealthy for Sensitive Groups 1 of 362 days1999: Good 319 of 364 days1999: Moderate 42 of 364 days1999: Unhealthy for Sensitive Groups 3 of 364 days2000: Good 348 of 366 days2000: Moderate 17 of 366 days2000: Unhealthy for Sensitive Groups 1 of 366 days20002001: Good 343 of 365 days2001: Moderate 22 of 365 days2002: Good 304 of 361 days2002: Moderate 50 of 361 days2002: Unhealthy for Sensitive Groups 6 of 361 days2002: Unhealthy 1 of 361 days2003: Good 331 of 363 days2003: Moderate 32 of 363 days2004: Good 343 of 362 days2004: Moderate 19 of 362 days2005: Good 350 of 361 days2005: Moderate 11 of 361 days20052006: Good 334 of 364 days2006: Moderate 29 of 364 days2006: Unhealthy for Sensitive Groups 1 of 364 days2007: Good 345 of 356 days2007: Moderate 11 of 356 days2008: Good 339 of 363 days2008: Moderate 21 of 363 days2008: Unhealthy for Sensitive Groups 1 of 363 days2008: Unhealthy 2 of 363 days2009: Good 349 of 362 days2009: Moderate 13 of 362 days2010: Good 356 of 361 days2010: Moderate 5 of 361 days20102011: Good 359 of 365 days2011: Moderate 6 of 365 days2012: Good 336 of 362 days2012: Moderate 23 of 362 days2012: Unhealthy for Sensitive Groups 3 of 362 days2013: Good 355 of 364 days2013: Moderate 9 of 364 days2014: Good 333 of 357 days2014: Moderate 24 of 357 days2015: Good 351 of 363 days2015: Moderate 11 of 363 days2015: Unhealthy for Sensitive Groups 1 of 363 days20152016: Good 356 of 365 days2016: Moderate 9 of 365 days2017: Good 350 of 362 days2017: Moderate 10 of 362 days2017: Unhealthy for Sensitive Groups 1 of 362 days2017: Unhealthy 1 of 362 days2018: Good 344 of 357 days2018: Moderate 10 of 357 days2018: Unhealthy for Sensitive Groups 1 of 357 days2018: Unhealthy 1 of 357 days2018: Very Unhealthy 1 of 357 days2019: Good 360 of 360 days2020: Good 341 of 351 days2020: Moderate 6 of 351 days2020: Unhealthy for Sensitive Groups 1 of 351 days2020: Unhealthy 3 of 351 days20202021: Good 348 of 356 days2021: Moderate 7 of 356 days2021: Unhealthy 1 of 356 days2022: Good 359 of 363 days2022: Moderate 4 of 363 days2023: Good 357 of 363 days2023: Moderate 6 of 363 days2024: Good 361 of 363 days2024: Moderate 2 of 363 days2025: Good 360 of 363 days2025: Moderate 3 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 year0501001980: 90th percentile AQI 611981: 90th percentile AQI 441982: 90th percentile AQI 471983: 90th percentile AQI 421984: 90th percentile AQI 471985: 90th percentile AQI 441986: 90th percentile AQI 471987: 90th percentile AQI 511988: 90th percentile AQI 381989: 90th percentile AQI 371990: 90th percentile AQI 401991: 90th percentile AQI 471992: 90th percentile AQI 391993: 90th percentile AQI 421994: 90th percentile AQI 581995: 90th percentile AQI 421996: 90th percentile AQI 421997: 90th percentile AQI 381998: 90th percentile AQI 391999: 90th percentile AQI 542000: 90th percentile AQI 462001: 90th percentile AQI 472002: 90th percentile AQI 582003: 90th percentile AQI 482004: 90th percentile AQI 472005: 90th percentile AQI 462006: 90th percentile AQI 482007: 90th percentile AQI 442008: 90th percentile AQI 462009: 90th percentile AQI 442010: 90th percentile AQI 442011: 90th percentile AQI 442012: 90th percentile AQI 482013: 90th percentile AQI 442014: 90th percentile AQI 482015: 90th percentile AQI 472016: 90th percentile AQI 442017: 90th percentile AQI 442018: 90th percentile AQI 432019: 90th percentile AQI 422020: 90th percentile AQI 442021: 90th percentile AQI 432022: 90th percentile AQI 432023: 90th percentile AQI 392024: 90th percentile AQI 412025: 90th percentile AQI 391980: Median AQI 341981: Median AQI 281982: Median AQI 321983: Median AQI 311984: Median AQI 311985: Median AQI 291986: Median AQI 291987: Median AQI 301988: Median AQI 261989: Median AQI 281990: Median AQI 271991: Median AQI 341992: Median AQI 281993: Median AQI 291994: Median AQI 391995: Median AQI 281996: Median AQI 281997: Median AQI 281998: Median AQI 281999: Median AQI 332000: Median AQI 342001: Median AQI 372002: Median AQI 372003: Median AQI 372004: Median AQI 352005: Median AQI 352006: Median AQI 372007: Median AQI 322008: Median AQI 342009: Median AQI 342010: Median AQI 352011: Median AQI 342012: Median AQI 352013: Median AQI 332014: Median AQI 372015: Median AQI 362016: Median AQI 332017: Median AQI 352018: Median AQI 332019: Median AQI 312020: Median AQI 322021: Median AQI 332022: Median AQI 322023: Median AQI 322024: Median AQI 322025: Median AQI 311980198519901995200020052010201520202025
  • 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
Ozone35297%
Fine particles (PM2.5)113%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
202536336030000313974Ozone
202436336120000324167Ozone
202336335760000323967Ozone
202236335940000324376Ozone
2021356348701003343157Ozone
2020351341613003244190Ozone
201936036000000314250Ozone
20183573441011103343233Ozone
20173623501011003544172Ozone
201636535690000334474Ozone
20153633511110003647148Ozone
2014357333240000374893Ozone
201336435590000334480Ozone
20123623362330003548143Ozone
201136535960000344454Ozone
201036135650000354474Ozone
2009362349130000344490Ozone
20083633392112003446180Ozone
2007356345110000324477Ozone
20063643342910003748101Ozone
2005361350110000354687Ozone
2004362343190000354787Ozone
2003363331320000374884Ozone
20023613045061003758164Ozone
2001365343220000374784Ozone
20003663481710003446108Ozone
19993643194230003354105Ozone
1998362357410002839119Ozone
199730930270000283884Ozone
1996361352900002842100Ozone
199536235750000284277Ozone
19943643085420003958115Ozone
1993359351710002942105Ozone
199228628420000283958Ozone
1991361341200000344787Ozone
199036536140000274077Ozone
198935535500000283749Ozone
198836335670000263871Ozone
19873573203430003051133Ozone
19863443182240002947133Ozone
19853603481200002944100Ozone
19843593342410003147122Ozone
198332231840000314271Ozone
19823363112320003247108Ozone
198135434770000284467Ozone
19802382033230003461115Ozone

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