EnviroNearby

Mariposa County, California air quality history

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

81%
Good days in 2025
44
Median daily AQI, 2025
0
Days above 100 in 2025
340
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Mariposa, California on 340 days. 274 of those days (81%) were in the Good range, and the median daily AQI was 44. That median is about the same as the typical monitored county in California (median 45.5 across 46 counties), and higher than 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 54% in 1987–1989 versus 70% in 2023–2025.

Years with fewer than 120 monitored days (1986) 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 5 of 10 days1986: Moderate 5 of 10 days19861987: Good 108 of 277 days1987: Moderate 99 of 277 days1987: Unhealthy for Sensitive Groups 51 of 277 days1987: Unhealthy 18 of 277 days1987: Very Unhealthy 1 of 277 days1988: Good 196 of 346 days1988: Moderate 79 of 346 days1988: Unhealthy for Sensitive Groups 54 of 346 days1988: Unhealthy 17 of 346 days1989: Good 241 of 357 days1989: Moderate 79 of 357 days1989: Unhealthy for Sensitive Groups 34 of 357 days1989: Unhealthy 3 of 357 days1990: Good 190 of 362 days1990: Moderate 101 of 362 days1990: Unhealthy for Sensitive Groups 52 of 362 days1990: Unhealthy 19 of 362 days1991: Good 218 of 358 days1991: Moderate 54 of 358 days1991: Unhealthy for Sensitive Groups 61 of 358 days1991: Unhealthy 25 of 358 days19911992: Good 199 of 366 days1992: Moderate 99 of 366 days1992: Unhealthy for Sensitive Groups 59 of 366 days1992: Unhealthy 9 of 366 days1993: Good 252 of 365 days1993: Moderate 87 of 365 days1993: Unhealthy for Sensitive Groups 26 of 365 days1994: Good 187 of 365 days1994: Moderate 96 of 365 days1994: Unhealthy for Sensitive Groups 71 of 365 days1994: Unhealthy 11 of 365 days1995: Good 201 of 365 days1995: Moderate 84 of 365 days1995: Unhealthy for Sensitive Groups 59 of 365 days1995: Unhealthy 21 of 365 days1996: Good 209 of 364 days1996: Moderate 57 of 364 days1996: Unhealthy for Sensitive Groups 71 of 364 days1996: Unhealthy 25 of 364 days1996: Very Unhealthy 2 of 364 days19961997: Good 198 of 361 days1997: Moderate 108 of 361 days1997: Unhealthy for Sensitive Groups 49 of 361 days1997: Unhealthy 6 of 361 days1998: Good 206 of 354 days1998: Moderate 82 of 354 days1998: Unhealthy for Sensitive Groups 52 of 354 days1998: Unhealthy 14 of 354 days1999: Good 156 of 355 days1999: Moderate 107 of 355 days1999: Unhealthy for Sensitive Groups 71 of 355 days1999: Unhealthy 21 of 355 days2000: Good 199 of 362 days2000: Moderate 93 of 362 days2000: Unhealthy for Sensitive Groups 58 of 362 days2000: Unhealthy 12 of 362 days2001: Good 187 of 346 days2001: Moderate 92 of 346 days2001: Unhealthy for Sensitive Groups 60 of 346 days2001: Unhealthy 7 of 346 days20012002: Good 130 of 364 days2002: Moderate 131 of 364 days2002: Unhealthy for Sensitive Groups 79 of 364 days2002: Unhealthy 24 of 364 days2003: Good 147 of 365 days2003: Moderate 113 of 365 days2003: Unhealthy for Sensitive Groups 82 of 365 days2003: Unhealthy 23 of 365 days2004: Good 112 of 366 days2004: Moderate 183 of 366 days2004: Unhealthy for Sensitive Groups 54 of 366 days2004: Unhealthy 12 of 366 days2004: Very Unhealthy 4 of 366 days2004: Hazardous 1 of 366 days2005: Good 40 of 365 days2005: Moderate 278 of 365 days2005: Unhealthy for Sensitive Groups 41 of 365 days2005: Unhealthy 6 of 365 days2006: Good 45 of 365 days2006: Moderate 256 of 365 days2006: Unhealthy for Sensitive Groups 58 of 365 days2006: Unhealthy 6 of 365 days20062007: Good 52 of 365 days2007: Moderate 261 of 365 days2007: Unhealthy for Sensitive Groups 45 of 365 days2007: Unhealthy 6 of 365 days2007: Very Unhealthy 1 of 365 days2008: Good 92 of 366 days2008: Moderate 213 of 366 days2008: Unhealthy for Sensitive Groups 45 of 366 days2008: Unhealthy 15 of 366 days2008: Very Unhealthy 1 of 366 days2009: Good 119 of 365 days2009: Moderate 212 of 365 days2009: Unhealthy for Sensitive Groups 33 of 365 days2009: Unhealthy 1 of 365 days2010: Good 152 of 365 days2010: Moderate 187 of 365 days2010: Unhealthy for Sensitive Groups 23 of 365 days2010: Unhealthy 3 of 365 days2011: Good 173 of 365 days2011: Moderate 164 of 365 days2011: Unhealthy for Sensitive Groups 28 of 365 days20112012: Good 132 of 366 days2012: Moderate 188 of 366 days2012: Unhealthy for Sensitive Groups 44 of 366 days2012: Unhealthy 2 of 366 days2013: Good 128 of 365 days2013: Moderate 215 of 365 days2013: Unhealthy for Sensitive Groups 21 of 365 days2013: Very Unhealthy 1 of 365 days2014: Good 160 of 365 days2014: Moderate 178 of 365 days2014: Unhealthy for Sensitive Groups 26 of 365 days2014: Unhealthy 1 of 365 days2015: Good 220 of 365 days2015: Moderate 134 of 365 days2015: Unhealthy for Sensitive Groups 6 of 365 days2015: Unhealthy 4 of 365 days2015: Very Unhealthy 1 of 365 days2016: Good 197 of 366 days2016: Moderate 149 of 366 days2016: Unhealthy for Sensitive Groups 19 of 366 days2016: Unhealthy 1 of 366 days20162017: Good 146 of 365 days2017: Moderate 179 of 365 days2017: Unhealthy for Sensitive Groups 31 of 365 days2017: Unhealthy 9 of 365 days2018: Good 156 of 365 days2018: Moderate 169 of 365 days2018: Unhealthy for Sensitive Groups 10 of 365 days2018: Unhealthy 13 of 365 days2018: Very Unhealthy 15 of 365 days2018: Hazardous 2 of 365 days2019: Good 192 of 365 days2019: Moderate 159 of 365 days2019: Unhealthy for Sensitive Groups 9 of 365 days2019: Unhealthy 5 of 365 days2020: Good 195 of 366 days2020: Moderate 123 of 366 days2020: Unhealthy for Sensitive Groups 27 of 366 days2020: Unhealthy 10 of 366 days2020: Very Unhealthy 6 of 366 days2020: Hazardous 5 of 366 days2021: Good 193 of 365 days2021: Moderate 140 of 365 days2021: Unhealthy for Sensitive Groups 25 of 365 days2021: Unhealthy 7 of 365 days20212022: Good 211 of 365 days2022: Moderate 125 of 365 days2022: Unhealthy for Sensitive Groups 8 of 365 days2022: Unhealthy 21 of 365 days2023: Good 217 of 365 days2023: Moderate 131 of 365 days2023: Unhealthy for Sensitive Groups 10 of 365 days2023: Unhealthy 5 of 365 days2023: Very Unhealthy 2 of 365 days2024: Good 255 of 366 days2024: Moderate 105 of 366 days2024: Unhealthy for Sensitive Groups 6 of 366 days2025: Good 274 of 340 days2025: Moderate 66 of 340 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 1401988: 90th percentile AQI 1331989: 90th percentile AQI 1011990: 90th percentile AQI 1261991: 90th percentile AQI 1431992: 90th percentile AQI 1191993: 90th percentile AQI 931994: 90th percentile AQI 1291995: 90th percentile AQI 1361996: 90th percentile AQI 1431997: 90th percentile AQI 1081998: 90th percentile AQI 1151999: 90th percentile AQI 1402000: 90th percentile AQI 1262001: 90th percentile AQI 1222002: 90th percentile AQI 1402003: 90th percentile AQI 1402004: 90th percentile AQI 1222005: 90th percentile AQI 1082006: 90th percentile AQI 1192007: 90th percentile AQI 1152008: 90th percentile AQI 1192009: 90th percentile AQI 1002010: 90th percentile AQI 932011: 90th percentile AQI 972012: 90th percentile AQI 1052013: 90th percentile AQI 902014: 90th percentile AQI 932015: 90th percentile AQI 842016: 90th percentile AQI 932017: 90th percentile AQI 1012018: 90th percentile AQI 1082019: 90th percentile AQI 842020: 90th percentile AQI 1112021: 90th percentile AQI 972022: 90th percentile AQI 892023: 90th percentile AQI 772024: 90th percentile AQI 742025: 90th percentile AQI 641986: Median AQI 531987: Median AQI 641988: Median AQI 461989: Median AQI 401990: Median AQI 491991: Median AQI 411992: Median AQI 461993: Median AQI 411994: Median AQI 501995: Median AQI 471996: Median AQI 451997: Median AQI 481998: Median AQI 461999: Median AQI 612000: Median AQI 482001: Median AQI 492002: Median AQI 612003: Median AQI 582004: Median AQI 642005: Median AQI 612006: Median AQI 642007: Median AQI 632008: Median AQI 592009: Median AQI 562010: Median AQI 522011: Median AQI 512012: Median AQI 582013: Median AQI 562014: Median AQI 532015: Median AQI 472016: Median AQI 482017: Median AQI 542018: Median AQI 532019: Median AQI 502020: Median AQI 492021: Median AQI 492022: Median AQI 482023: Median AQI 472024: Median AQI 452025: Median AQI 44198619911996200120062011201620212025
  • 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
Ozone33899%
Fine particles (PM2.5)21%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
2025340274660000446490Ozone
202436625510560004574133Ozone
2023365217131105204777264Ozone
2022365211125821004889198Ozone
2021365193140257004997162Ozone
2020366195123271065491111073Ozone
201936519215995005084185Ozone
2018365156169101315253108352Ozone
20173651461793190054101189Ozone
2016366197149191004893159Ozone
201536522013464104784240Ozone
2014365160178261005393153Ozone
2013365128215210105690255Ozone
20123661321884420058105166Ozone
2011365173164280005197150Ozone
2010365152187233005293187Ozone
20093651192123310056100151Ozone
20083669221345151059119206Ozone
2007365522614561063115209PM2.5
2006365452565860064119172PM2.5
2005365402784160061108177PM2.5
200436611218354124164122352Ozone
200336514711382230058140195Ozone
200236413013179240061140179Ozone
2001346187926070049122182Ozone
20003621999358120048126187Ozone
199935515610771210061140200Ozone
19983542068252140046115195Ozone
19973611981084960048108200Ozone
19963642095771252045143202Ozone
19953652018459210047136195Ozone
19943651879671110050129197Ozone
199336525287260004193136Ozone
1992366199995990046119174Ozone
19913582185461250041143198Ozone
199036219010152190049126177Ozone
1989357241793430040101166Ozone
19883461967954170046133177Ozone
19872771089951181064140206Ozone
198610550000536969PM10

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