EnviroNearby

Santa Cruz County, California air quality history

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

88%
Good days in 2025
35
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 Santa Cruz, California on 365 days. 320 of those days (88%) were in the Good range, and the median daily AQI was 35. 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 192 days. Across the years with fuller monitoring, the share of Good days fell: an average of 90% in 1980–1982 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 325 of 366 days1980: Moderate 36 of 366 days1980: Unhealthy for Sensitive Groups 4 of 366 days1980: Unhealthy 1 of 366 days19801981: Good 329 of 365 days1981: Moderate 31 of 365 days1981: Unhealthy for Sensitive Groups 5 of 365 days1982: Good 332 of 364 days1982: Moderate 27 of 364 days1982: Unhealthy for Sensitive Groups 5 of 364 days1983: Good 354 of 364 days1983: Moderate 9 of 364 days1983: Unhealthy for Sensitive Groups 1 of 364 days1984: Good 341 of 353 days1984: Moderate 11 of 353 days1984: Unhealthy for Sensitive Groups 1 of 353 days1985: Good 328 of 359 days1985: Moderate 27 of 359 days1985: Unhealthy for Sensitive Groups 3 of 359 days1985: Unhealthy 1 of 359 days19851986: Good 339 of 350 days1986: Moderate 10 of 350 days1986: Unhealthy for Sensitive Groups 1 of 350 days1987: Good 343 of 365 days1987: Moderate 20 of 365 days1987: Unhealthy for Sensitive Groups 2 of 365 days1988: Good 341 of 359 days1988: Moderate 18 of 359 days1989: Good 345 of 364 days1989: Moderate 16 of 364 days1989: Unhealthy for Sensitive Groups 2 of 364 days1989: Unhealthy 1 of 364 days1990: Good 357 of 365 days1990: Moderate 7 of 365 days1990: Unhealthy for Sensitive Groups 1 of 365 days19901991: Good 357 of 365 days1991: Moderate 6 of 365 days1991: Unhealthy for Sensitive Groups 2 of 365 days1992: Good 359 of 366 days1992: Moderate 7 of 366 days1993: Good 346 of 360 days1993: Moderate 13 of 360 days1993: Unhealthy for Sensitive Groups 1 of 360 days1994: Good 343 of 365 days1994: Moderate 18 of 365 days1994: Unhealthy for Sensitive Groups 4 of 365 days1995: Good 340 of 365 days1995: Moderate 25 of 365 days19951996: Good 324 of 366 days1996: Moderate 36 of 366 days1996: Unhealthy for Sensitive Groups 4 of 366 days1996: Unhealthy 2 of 366 days1997: Good 343 of 365 days1997: Moderate 21 of 365 days1997: Unhealthy for Sensitive Groups 1 of 365 days1998: Good 343 of 365 days1998: Moderate 21 of 365 days1998: Unhealthy for Sensitive Groups 1 of 365 days1999: Good 294 of 365 days1999: Moderate 68 of 365 days1999: Unhealthy for Sensitive Groups 3 of 365 days2000: Good 332 of 366 days2000: Moderate 33 of 366 days2000: Unhealthy for Sensitive Groups 1 of 366 days20002001: Good 327 of 365 days2001: Moderate 36 of 365 days2001: Unhealthy for Sensitive Groups 2 of 365 days2002: Good 316 of 365 days2002: Moderate 48 of 365 days2002: Unhealthy for Sensitive Groups 1 of 365 days2003: Good 328 of 365 days2003: Moderate 35 of 365 days2003: Unhealthy for Sensitive Groups 2 of 365 days2004: Good 341 of 366 days2004: Moderate 22 of 366 days2004: Unhealthy for Sensitive Groups 3 of 366 days2005: Good 347 of 365 days2005: Moderate 18 of 365 days20052006: Good 338 of 365 days2006: Moderate 26 of 365 days2006: Unhealthy for Sensitive Groups 1 of 365 days2007: Good 347 of 365 days2007: Moderate 18 of 365 days2008: Good 326 of 366 days2008: Moderate 39 of 366 days2008: Unhealthy for Sensitive Groups 1 of 366 days2009: Good 351 of 365 days2009: Moderate 14 of 365 days2010: Good 311 of 365 days2010: Moderate 54 of 365 days20102011: Good 293 of 365 days2011: Moderate 72 of 365 days2012: Good 328 of 365 days2012: Moderate 36 of 365 days2012: Unhealthy for Sensitive Groups 1 of 365 days2013: Good 249 of 365 days2013: Moderate 94 of 365 days2013: Unhealthy for Sensitive Groups 22 of 365 days2014: Good 256 of 365 days2014: Moderate 97 of 365 days2014: Unhealthy for Sensitive Groups 12 of 365 days2015: Good 282 of 365 days2015: Moderate 83 of 365 days20152016: Good 306 of 366 days2016: Moderate 60 of 366 days2017: Good 269 of 365 days2017: Moderate 92 of 365 days2017: Unhealthy for Sensitive Groups 4 of 365 days2018: Good 273 of 365 days2018: Moderate 82 of 365 days2018: Unhealthy for Sensitive Groups 5 of 365 days2018: Unhealthy 5 of 365 days2019: Good 291 of 365 days2019: Moderate 74 of 365 days2020: Good 261 of 366 days2020: Moderate 85 of 366 days2020: Unhealthy for Sensitive Groups 6 of 366 days2020: Unhealthy 10 of 366 days2020: Very Unhealthy 1 of 366 days2020: Hazardous 3 of 366 days20202021: Good 298 of 365 days2021: Moderate 67 of 365 days2022: Good 287 of 365 days2022: Moderate 78 of 365 days2023: Good 300 of 365 days2023: Moderate 64 of 365 days2023: Unhealthy for Sensitive Groups 1 of 365 days2024: Good 293 of 366 days2024: Moderate 73 of 366 days2025: Good 320 of 365 days2025: Moderate 45 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 491982: 90th percentile AQI 491983: 90th percentile AQI 421984: 90th percentile AQI 421985: 90th percentile AQI 481986: 90th percentile AQI 431987: 90th percentile AQI 461988: 90th percentile AQI 461989: 90th percentile AQI 441990: 90th percentile AQI 441991: 90th percentile AQI 441992: 90th percentile AQI 431993: 90th percentile AQI 441994: 90th percentile AQI 471995: 90th percentile AQI 471996: 90th percentile AQI 541997: 90th percentile AQI 461998: 90th percentile AQI 461999: 90th percentile AQI 572000: 90th percentile AQI 502001: 90th percentile AQI 512002: 90th percentile AQI 542003: 90th percentile AQI 512004: 90th percentile AQI 472005: 90th percentile AQI 452006: 90th percentile AQI 472007: 90th percentile AQI 452008: 90th percentile AQI 512009: 90th percentile AQI 442010: 90th percentile AQI 532011: 90th percentile AQI 542012: 90th percentile AQI 512013: 90th percentile AQI 842014: 90th percentile AQI 702015: 90th percentile AQI 592016: 90th percentile AQI 542017: 90th percentile AQI 612018: 90th percentile AQI 562019: 90th percentile AQI 542020: 90th percentile AQI 682021: 90th percentile AQI 542022: 90th percentile AQI 562023: 90th percentile AQI 532024: 90th percentile AQI 542025: 90th percentile AQI 531980: Median AQI 381981: Median AQI 351982: Median AQI 341983: Median AQI 301984: Median AQI 311985: Median AQI 331986: Median AQI 281987: Median AQI 321988: Median AQI 331989: Median AQI 341990: Median AQI 321991: Median AQI 341992: Median AQI 321993: Median AQI 311994: Median AQI 351995: Median AQI 361996: Median AQI 361997: Median AQI 351998: Median AQI 361999: Median AQI 372000: Median AQI 372001: Median AQI 362002: Median AQI 362003: Median AQI 362004: Median AQI 362005: Median AQI 342006: Median AQI 372007: Median AQI 342008: Median AQI 362009: Median AQI 312010: Median AQI 372011: Median AQI 412012: Median AQI 362013: Median AQI 422014: Median AQI 392015: Median AQI 382016: Median AQI 352017: Median AQI 392018: Median AQI 412019: Median AQI 392020: Median AQI 392021: Median AQI 372022: Median AQI 352023: Median AQI 362024: Median AQI 392025: Median AQI 351980198519901995200020052010201520202025
  • 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
Ozone19253%
Fine particles (PM2.5)17347%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
2025365320450000355371Ozone
2024366293730000395480PM2.5
20233653006410003653130PM2.5
2022365287780000355693PM2.5
2021365298670000375480Ozone
202036626185610133968624PM2.5
2019365291740000395474PM2.5
20183652738255004156177PM2.5
20173652699240003961130PM2.5
2016366306600000355476PM2.5
2015365282830000385995Ozone
201436525697120003970136Ozone
201336524994220004284149PM2.5
20123653283610003651101Ozone
2011365293720000415480PM2.5
2010365311540000375395PM2.5
2009365351140000314487Ozone
20083663263910003651115Ozone
2007365347180000344597Ozone
20063653382610003747101Ozone
2005365347180000344587Ozone
20043663412230003647143Ozone
20033653283520003651112Ozone
20023653164810003654122Ozone
20013653273620003651108Ozone
20003663323310003750126Ozone
19993652946830003757105Ozone
19983653432110003646122Ozone
19973653432110003546101Ozone
19963663243642003654156Ozone
19953653402500003647100Ozone
19943653431840003547126Ozone
19933603461310003144105Ozone
1992366359700003243100Ozone
1991365357620003444140Ozone
1990365357710003244133Ozone
19893643451621003444154Ozone
19883593411800003346100Ozone
19873653432020003246108Ozone
19863503391010002843122Ozone
19853593282731003348156Ozone
19843533411110003142105Ozone
1983364354910003042101Ozone
19823643322750003449108Ozone
19813653293150003549133Ozone
19803663253641003857156Ozone

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