EnviroNearby

Navajo County, Arizona air quality history

Daily Air Quality Index summaries from EPA monitors in Navajo, Arizona, 1986–2025.

99%
Good days in 2025
13
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 Navajo, Arizona on 365 days. 363 of those days (99%) were in the Good range, and the median daily AQI was 13. That median is lower than the typical monitored county in Arizona (median 47 across 13 counties), and lower than the typical monitored U.S. county (40). The main pollutant was coarse particles (PM10) on 290 days. Across the years with fuller monitoring, the share of Good days held roughly steady: an average of 95% in 1989–1991 versus 93% in 2023–2025.

Years with fewer than 120 monitored days (1992, 1993, 1995, 1997, 1998, 2001…) 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 21 of 22 days1986: Moderate 1 of 22 days19861987: Good 40 of 41 days1987: Moderate 1 of 41 days1988: Good 114 of 119 days1988: Moderate 5 of 119 days1989: Good 130 of 134 days1989: Moderate 4 of 134 days1990: Good 121 of 132 days1990: Moderate 11 of 132 days1991: Good 124 of 128 days1991: Moderate 4 of 128 days19911992: Good 107 of 110 days1992: Moderate 3 of 110 days1993: Good 117 of 117 days1994: Good 128 of 130 days1994: Moderate 2 of 130 days1995: Good 114 of 116 days1995: Moderate 2 of 116 days1996: Good 131 of 132 days1996: Moderate 1 of 132 days19961997: Good 112 of 116 days1997: Moderate 4 of 116 days1998: Good 92 of 92 days1999: Good 132 of 134 days1999: Moderate 2 of 134 days2000: Good 120 of 120 days2001: Good 106 of 107 days2001: Moderate 1 of 107 days20012002: Good 164 of 171 days2002: Moderate 7 of 171 days2003: Good 201 of 354 days2003: Moderate 145 of 354 days2003: Unhealthy for Sensitive Groups 8 of 354 days2004: Good 216 of 335 days2004: Moderate 115 of 335 days2004: Unhealthy for Sensitive Groups 4 of 335 days2005: Good 217 of 332 days2005: Moderate 112 of 332 days2005: Unhealthy for Sensitive Groups 3 of 332 days2006: Good 230 of 328 days2006: Moderate 92 of 328 days2006: Unhealthy for Sensitive Groups 6 of 328 days20062007: Good 198 of 311 days2007: Moderate 111 of 311 days2007: Unhealthy for Sensitive Groups 2 of 311 days2008: Good 218 of 345 days2008: Moderate 122 of 345 days2008: Unhealthy for Sensitive Groups 5 of 345 days2009: Good 278 of 365 days2009: Moderate 87 of 365 days2010: Good 279 of 364 days2010: Moderate 83 of 364 days2010: Unhealthy for Sensitive Groups 2 of 364 days2011: Good 246 of 365 days2011: Moderate 118 of 365 days2011: Unhealthy for Sensitive Groups 1 of 365 days20112012: Good 245 of 366 days2012: Moderate 114 of 366 days2012: Unhealthy for Sensitive Groups 7 of 366 days2013: Good 246 of 365 days2013: Moderate 119 of 365 days2014: Good 272 of 365 days2014: Moderate 91 of 365 days2014: Unhealthy for Sensitive Groups 2 of 365 days2015: Good 316 of 365 days2015: Moderate 49 of 365 days2016: Good 299 of 366 days2016: Moderate 67 of 366 days20162017: Good 278 of 365 days2017: Moderate 86 of 365 days2017: Unhealthy for Sensitive Groups 1 of 365 days2018: Good 260 of 363 days2018: Moderate 101 of 363 days2018: Unhealthy for Sensitive Groups 2 of 363 days2019: Good 294 of 365 days2019: Moderate 70 of 365 days2019: Unhealthy for Sensitive Groups 1 of 365 days2020: Good 314 of 366 days2020: Moderate 50 of 366 days2020: Unhealthy for Sensitive Groups 2 of 366 days2021: Good 292 of 365 days2021: Moderate 72 of 365 days2021: Unhealthy for Sensitive Groups 1 of 365 days20212022: Good 307 of 364 days2022: Moderate 57 of 364 days2023: Good 290 of 364 days2023: Moderate 74 of 364 days2024: Good 359 of 361 days2024: Moderate 2 of 361 days2025: Good 363 of 365 days2025: Moderate 2 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 year0501001986: 90th percentile AQI 441987: 90th percentile AQI 401988: 90th percentile AQI 391989: 90th percentile AQI 381990: 90th percentile AQI 451991: 90th percentile AQI 341992: 90th percentile AQI 341993: 90th percentile AQI 321994: 90th percentile AQI 321995: 90th percentile AQI 331996: 90th percentile AQI 291997: 90th percentile AQI 361998: 90th percentile AQI 321999: 90th percentile AQI 322000: 90th percentile AQI 292001: 90th percentile AQI 322002: 90th percentile AQI 472003: 90th percentile AQI 842004: 90th percentile AQI 802005: 90th percentile AQI 772006: 90th percentile AQI 742007: 90th percentile AQI 772008: 90th percentile AQI 772009: 90th percentile AQI 612010: 90th percentile AQI 612011: 90th percentile AQI 742012: 90th percentile AQI 802013: 90th percentile AQI 742014: 90th percentile AQI 642015: 90th percentile AQI 542016: 90th percentile AQI 542017: 90th percentile AQI 642018: 90th percentile AQI 742019: 90th percentile AQI 582020: 90th percentile AQI 542021: 90th percentile AQI 612022: 90th percentile AQI 582023: 90th percentile AQI 642024: 90th percentile AQI 222025: 90th percentile AQI 241986: Median AQI 231987: Median AQI 191988: Median AQI 221989: Median AQI 221990: Median AQI 231991: Median AQI 211992: Median AQI 201993: Median AQI 181994: Median AQI 171995: Median AQI 181996: Median AQI 131997: Median AQI 181998: Median AQI 171999: Median AQI 192000: Median AQI 152001: Median AQI 162002: Median AQI 332003: Median AQI 482004: Median AQI 462005: Median AQI 442006: Median AQI 452007: Median AQI 462008: Median AQI 472009: Median AQI 442010: Median AQI 442011: Median AQI 462012: Median AQI 452013: Median AQI 462014: Median AQI 442015: Median AQI 392016: Median AQI 432017: Median AQI 442018: Median AQI 442019: Median AQI 442020: Median AQI 432021: Median AQI 442022: Median AQI 442023: Median AQI 432024: Median AQI 132025: Median AQI 13198619911996200120062011201620212025
  • 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
Coarse particles (PM10)29079%
Fine particles (PM2.5)7521%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
202536536320000132454PM10
202436135920000132253PM10
2023364290740000436484Ozone
2022364307570000445893Ozone
20213652927210004461101Ozone
20203663145020004354136Ozone
20193652947010004458112Ozone
201836326010120004474115Ozone
20173652788610004464101Ozone
2016366299670000435490Ozone
20153653164900003954100Ozone
20143652729120004464101Ozone
201336524611900004674100Ozone
201236624511470004580126Ozone
201136524611810004674105Ozone
20103642798320004461112Ozone
2009365278870000446197Ozone
200834521812250004777115Ozone
200731119811120004677112Ozone
20063282309260004574150Ozone
200533221711230004477140Ozone
200433521611540004680147Ozone
200335420114580004884122Ozone
200217116470000334764Ozone
200110710610000163252PM2.5
200012012000000152949PM2.5
199913413220000193262PM2.5
1998929200000173243PM2.5
199711611240000183687PM2.5
199613213110000132953PM2.5
199511611420000183353PM2.5
199413012820000173264PM2.5
199311711700000183243PM2.5
199211010730000203473PM2.5
199112812440000213457PM2.5
1990132121110000234571PM2.5
198913413040000223865PM2.5
198811911450000223976PM2.5
1987414010000194078PM10
1986222110000234462PM10

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 Arizona with a similar median AQI in 2025

All monitored counties in Arizona

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