EnviroNearby

Monterey County, California air quality history

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

86%
Good days in 2025
38
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 Monterey, California on 365 days. 314 of those days (86%) 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 175 days. Across the years with fuller monitoring, the share of Good days fell: an average of 92% in 1980–1982 versus 80% 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 318 of 366 days1980: Moderate 40 of 366 days1980: Unhealthy for Sensitive Groups 5 of 366 days1980: Unhealthy 2 of 366 days1980: Very Unhealthy 1 of 366 days19801981: Good 342 of 365 days1981: Moderate 23 of 365 days1982: Good 343 of 365 days1982: Moderate 20 of 365 days1982: Unhealthy for Sensitive Groups 2 of 365 days1983: Good 338 of 365 days1983: Moderate 22 of 365 days1983: Unhealthy for Sensitive Groups 5 of 365 days1984: Good 335 of 366 days1984: Moderate 26 of 366 days1984: Unhealthy for Sensitive Groups 5 of 366 days1985: Good 321 of 365 days1985: Moderate 35 of 365 days1985: Unhealthy for Sensitive Groups 8 of 365 days1985: Unhealthy 1 of 365 days19851986: Good 321 of 365 days1986: Moderate 39 of 365 days1986: Unhealthy for Sensitive Groups 5 of 365 days1987: Good 322 of 365 days1987: Moderate 39 of 365 days1987: Unhealthy for Sensitive Groups 4 of 365 days1988: Good 290 of 305 days1988: Moderate 13 of 305 days1988: Unhealthy for Sensitive Groups 2 of 305 days1989: Good 315 of 365 days1989: Moderate 41 of 365 days1989: Unhealthy for Sensitive Groups 8 of 365 days1989: Unhealthy 1 of 365 days1990: Good 312 of 365 days1990: Moderate 46 of 365 days1990: Unhealthy for Sensitive Groups 7 of 365 days19901991: Good 283 of 365 days1991: Moderate 77 of 365 days1991: Unhealthy for Sensitive Groups 5 of 365 days1992: Good 331 of 366 days1992: Moderate 32 of 366 days1992: Unhealthy for Sensitive Groups 3 of 366 days1993: Good 328 of 365 days1993: Moderate 29 of 365 days1993: Unhealthy for Sensitive Groups 8 of 365 days1994: Good 351 of 365 days1994: Moderate 10 of 365 days1994: Unhealthy for Sensitive Groups 3 of 365 days1994: Unhealthy 1 of 365 days1995: Good 339 of 365 days1995: Moderate 25 of 365 days1995: Unhealthy for Sensitive Groups 1 of 365 days19951996: Good 313 of 366 days1996: Moderate 42 of 366 days1996: Unhealthy for Sensitive Groups 11 of 366 days1997: Good 348 of 365 days1997: Moderate 15 of 365 days1997: Unhealthy for Sensitive Groups 2 of 365 days1998: Good 342 of 365 days1998: Moderate 22 of 365 days1998: Unhealthy for Sensitive Groups 1 of 365 days1999: Good 294 of 365 days1999: Moderate 70 of 365 days1999: Unhealthy for Sensitive Groups 1 of 365 days2000: Good 328 of 366 days2000: Moderate 35 of 366 days2000: Unhealthy for Sensitive Groups 3 of 366 days20002001: Good 331 of 365 days2001: Moderate 32 of 365 days2001: Unhealthy for Sensitive Groups 2 of 365 days2002: Good 314 of 365 days2002: Moderate 50 of 365 days2002: Unhealthy for Sensitive Groups 1 of 365 days2003: Good 329 of 365 days2003: Moderate 33 of 365 days2003: Unhealthy for Sensitive Groups 3 of 365 days2004: Good 335 of 366 days2004: Moderate 28 of 366 days2004: Unhealthy for Sensitive Groups 3 of 366 days2005: Good 344 of 365 days2005: Moderate 21 of 365 days20052006: Good 332 of 365 days2006: Moderate 32 of 365 days2006: Unhealthy for Sensitive Groups 1 of 365 days2007: Good 342 of 365 days2007: Moderate 23 of 365 days2008: Good 328 of 366 days2008: Moderate 38 of 366 days2009: Good 351 of 365 days2009: Moderate 13 of 365 days2009: Unhealthy for Sensitive Groups 1 of 365 days2010: Good 292 of 365 days2010: Moderate 73 of 365 days20102011: Good 293 of 365 days2011: Moderate 72 of 365 days2012: Good 285 of 366 days2012: Moderate 81 of 366 days2013: Good 251 of 365 days2013: Moderate 114 of 365 days2014: Good 285 of 365 days2014: Moderate 80 of 365 days2015: Good 285 of 365 days2015: Moderate 79 of 365 days2015: Unhealthy for Sensitive Groups 1 of 365 days20152016: Good 290 of 366 days2016: Moderate 65 of 366 days2016: Unhealthy for Sensitive Groups 3 of 366 days2016: Unhealthy 8 of 366 days2017: Good 265 of 365 days2017: Moderate 99 of 365 days2017: Unhealthy for Sensitive Groups 1 of 365 days2018: Good 258 of 365 days2018: Moderate 100 of 365 days2018: Unhealthy for Sensitive Groups 5 of 365 days2018: Unhealthy 2 of 365 days2019: Good 303 of 365 days2019: Moderate 61 of 365 days2019: Unhealthy for Sensitive Groups 1 of 365 days2020: Good 259 of 366 days2020: Moderate 92 of 366 days2020: Unhealthy for Sensitive Groups 4 of 366 days2020: Unhealthy 8 of 366 days2020: Very Unhealthy 3 of 366 days20202021: Good 261 of 365 days2021: Moderate 104 of 365 days2022: Good 299 of 365 days2022: Moderate 66 of 365 days2023: Good 274 of 365 days2023: Moderate 90 of 365 days2023: Unhealthy for Sensitive Groups 1 of 365 days2024: Good 292 of 366 days2024: Moderate 74 of 366 days2025: Good 314 of 365 days2025: Moderate 51 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 year0501001980: 90th percentile AQI 571981: 90th percentile AQI 471982: 90th percentile AQI 471983: 90th percentile AQI 471984: 90th percentile AQI 471985: 90th percentile AQI 571986: 90th percentile AQI 571987: 90th percentile AQI 541988: 90th percentile AQI 441989: 90th percentile AQI 571990: 90th percentile AQI 581991: 90th percentile AQI 611992: 90th percentile AQI 481993: 90th percentile AQI 511994: 90th percentile AQI 451995: 90th percentile AQI 481996: 90th percentile AQI 641997: 90th percentile AQI 451998: 90th percentile AQI 481999: 90th percentile AQI 622000: 90th percentile AQI 512001: 90th percentile AQI 492002: 90th percentile AQI 542003: 90th percentile AQI 502004: 90th percentile AQI 492005: 90th percentile AQI 462006: 90th percentile AQI 492007: 90th percentile AQI 472008: 90th percentile AQI 512009: 90th percentile AQI 442010: 90th percentile AQI 552011: 90th percentile AQI 542012: 90th percentile AQI 552013: 90th percentile AQI 572014: 90th percentile AQI 552015: 90th percentile AQI 542016: 90th percentile AQI 552017: 90th percentile AQI 582018: 90th percentile AQI 572019: 90th percentile AQI 542020: 90th percentile AQI 642021: 90th percentile AQI 572022: 90th percentile AQI 542023: 90th percentile AQI 552024: 90th percentile AQI 552025: 90th percentile AQI 531980: Median AQI 371981: Median AQI 371982: Median AQI 341983: Median AQI 371984: Median AQI 371985: Median AQI 381986: Median AQI 371987: Median AQI 371988: Median AQI 301989: Median AQI 381990: Median AQI 391991: Median AQI 441992: Median AQI 381993: Median AQI 351994: Median AQI 351995: Median AQI 351996: Median AQI 391997: Median AQI 351998: Median AQI 371999: Median AQI 392000: Median AQI 362001: Median AQI 352002: Median AQI 372003: Median AQI 372004: Median AQI 352005: Median AQI 352006: Median AQI 382007: Median AQI 352008: Median AQI 372009: Median AQI 332010: Median AQI 402011: Median AQI 412012: Median AQI 412013: Median AQI 442014: Median AQI 402015: Median AQI 412016: Median AQI 372017: Median AQI 412018: Median AQI 422019: Median AQI 392020: Median AQI 392021: Median AQI 412022: Median AQI 392023: Median AQI 422024: Median AQI 392025: Median AQI 381980198519901995200020052010201520202025
  • 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
Ozone17548%
Fine particles (PM2.5)16144%
Coarse particles (PM10)298%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
2025365314510000385362Ozone
2024366292740000395571Ozone
20233652749010004255115PM2.5
2022365299660000395480Ozone
20213652611040000415780PM2.5
20203662599248303964275PM2.5
20193653036110003954144Ozone
201836525810052004257157PM2.5
20173652659910004158121Ozone
20163662906538003755185Ozone
20153652857910004154120PM2.5
20143652858000004055100Ozone
20133652511140000445797PM2.5
2012366285810000415584PM2.5
2011365293720000415477Ozone
20103652927300004055100Ozone
20093653511310003344140Ozone
2008366328380000375197Ozone
20073653422300003547100Ozone
20063653323210003849126Ozone
2005365344210000354684Ozone
20043663352830003549129Ozone
20033653293330003750136Ozone
20023653145010003754108Ozone
20013653313220003549129Ozone
20003663283530003651129Ozone
19993652947010003962105Ozone
19983653422210003748119Ozone
19973653481520003545119Ozone
199636631342110003964136Ozone
19953653392510003548122Ozone
19943653511031003545166Ozone
19933653282980003551143Ozone
19923663313230003848150Ozone
19913652837750004461126Ozone
19903653124670003958133Ozone
19893653154181003857174Ozone
19883052901320003044122Ozone
19873653223940003754122Ozone
19863653213950003757119Ozone
19853653213581003857154Ozone
19843663352650003747115Ozone
19833653382250003747143Ozone
19823653432020003447108Ozone
19813653422300003747100Ozone
19803663184052103757203Ozone

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