EnviroNearby

Adams County, Washington air quality history

Daily Air Quality Index summaries from EPA monitors in Adams, Washington, 1993–2025.

91%
Good days in 2025
21
Median daily AQI, 2025
0
Days above 100 in 2025
348
Days with an AQI in 2025 (of 365)

In 2025, EPA reported a daily Air Quality Index (AQI) for Adams, Washington on 348 days. 315 of those days (91%) were in the Good range, and the median daily AQI was 21. That median is lower than the typical monitored county in Washington (median 28 across 30 counties), and lower than the typical monitored U.S. county (40). The main pollutant was fine particles (PM2.5) on 348 days. Across the years with fuller monitoring, the share of Good days rose: an average of 77% in 2002–2004 versus 91% in 2023–2025.

Years with fewer than 120 monitored days (1993, 1994, 1995, 2000, 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%1993: Good 47 of 56 days1993: Moderate 8 of 56 days1993: Unhealthy for Sensitive Groups 1 of 56 days19931994: Good 52 of 56 days1994: Moderate 4 of 56 days1995: Good 25 of 25 days2000: Good 4 of 11 days2000: Moderate 7 of 11 days2001: Good 46 of 56 days2001: Moderate 10 of 56 days2002: Good 86 of 122 days2002: Moderate 36 of 122 days20022003: Good 303 of 365 days2003: Moderate 61 of 365 days2003: Unhealthy for Sensitive Groups 1 of 365 days2004: Good 289 of 366 days2004: Moderate 77 of 366 days2005: Good 329 of 365 days2005: Moderate 36 of 365 days2006: Good 310 of 365 days2006: Moderate 55 of 365 days2007: Good 307 of 365 days2007: Moderate 58 of 365 days20072008: Good 301 of 360 days2008: Moderate 59 of 360 days2009: Good 336 of 365 days2009: Moderate 29 of 365 days2010: Good 317 of 336 days2010: Moderate 19 of 336 days2011: Good 332 of 363 days2011: Moderate 31 of 363 days2012: Good 330 of 366 days2012: Moderate 36 of 366 days20122013: Good 323 of 342 days2013: Moderate 19 of 342 days2014: Good 317 of 346 days2014: Moderate 29 of 346 days2015: Good 294 of 356 days2015: Moderate 57 of 356 days2015: Unhealthy for Sensitive Groups 2 of 356 days2015: Unhealthy 3 of 356 days2016: Good 339 of 346 days2016: Moderate 7 of 346 days2017: Good 316 of 357 days2017: Moderate 30 of 357 days2017: Unhealthy for Sensitive Groups 5 of 357 days2017: Unhealthy 4 of 357 days2017: Very Unhealthy 2 of 357 days20172018: Good 295 of 350 days2018: Moderate 47 of 350 days2018: Unhealthy for Sensitive Groups 4 of 350 days2018: Unhealthy 4 of 350 days2019: Good 339 of 360 days2019: Moderate 21 of 360 days2020: Good 345 of 364 days2020: Moderate 11 of 364 days2020: Unhealthy 5 of 364 days2020: Very Unhealthy 3 of 364 days2021: Good 333 of 364 days2021: Moderate 24 of 364 days2021: Unhealthy for Sensitive Groups 3 of 364 days2021: Unhealthy 4 of 364 days2022: Good 327 of 365 days2022: Moderate 34 of 365 days2022: Unhealthy for Sensitive Groups 2 of 365 days2022: Unhealthy 2 of 365 days20222023: Good 330 of 365 days2023: Moderate 32 of 365 days2023: Unhealthy for Sensitive Groups 1 of 365 days2023: Very Unhealthy 2 of 365 days2024: Good 328 of 351 days2024: Moderate 23 of 351 days2025: Good 315 of 348 days2025: Moderate 33 of 348 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 year0501001993: 90th percentile AQI 541994: 90th percentile AQI 471995: 90th percentile AQI 312000: 90th percentile AQI 692001: 90th percentile AQI 552002: 90th percentile AQI 592003: 90th percentile AQI 542004: 90th percentile AQI 542005: 90th percentile AQI 502006: 90th percentile AQI 542007: 90th percentile AQI 552008: 90th percentile AQI 542009: 90th percentile AQI 452010: 90th percentile AQI 422011: 90th percentile AQI 472012: 90th percentile AQI 502013: 90th percentile AQI 412014: 90th percentile AQI 442015: 90th percentile AQI 552016: 90th percentile AQI 332017: 90th percentile AQI 522018: 90th percentile AQI 582019: 90th percentile AQI 422020: 90th percentile AQI 432021: 90th percentile AQI 452022: 90th percentile AQI 522023: 90th percentile AQI 502024: 90th percentile AQI 412025: 90th percentile AQI 501993: Median AQI 261994: Median AQI 211995: Median AQI 152000: Median AQI 552001: Median AQI 332002: Median AQI 342003: Median AQI 322004: Median AQI 332005: Median AQI 292006: Median AQI 292007: Median AQI 282008: Median AQI 292009: Median AQI 282010: Median AQI 232011: Median AQI 242012: Median AQI 212013: Median AQI 202014: Median AQI 212015: Median AQI 272016: Median AQI 192017: Median AQI 182018: Median AQI 172019: Median AQI 172020: Median AQI 172021: Median AQI 192022: Median AQI 182023: Median AQI 212024: Median AQI 182025: Median AQI 211993200220072012201720222025
  • 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
Fine particles (PM2.5)348100%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
2025348315330000215099PM2.5
2024351328230000184171PM2.5
20233653303210202150267PM2.5
20223653273422001852162PM2.5
20213643332434001945191PM2.5
20203643451105301743266PM2.5
2019360339210000174289PM2.5
20183502954744001758195PM2.5
20173573163054201852207PM2.5
201634633970000193358PM2.5
20153562945723002755165PM2.5
2014346317290000214476PM2.5
2013342323190000204163PM2.5
2012366330360000215089PM2.5
2011363332310000244764PM2.5
2010336317190000234279PM2.5
2009365336290000284563PM2.5
2008360301590000295474PM2.5
2007365307580000285575PM2.5
2006365310550000295491PM2.5
2005365329360000295068PM2.5
2004366289770000335485PM2.5
20033653036110003254104PM2.5
200212286360000345968PM2.5
20015646100000335560PM2.5
200011470000556975PM2.5
1995252500000153131PM10
1994565240000214754PM10
19935647810002654135PM10

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 Washington with a similar median AQI in 2025

All monitored counties in Washington

Source: U.S. EPA AirData, “Annual AQI by County” files for 1993–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem