EnviroNearby

Columbia County, Washington air quality history

Daily Air Quality Index summaries from EPA monitors in Columbia, Washington, 2003–2025.

90%
Good days in 2025
36
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 Columbia, Washington on 365 days. 330 of those days (90%) were in the Good range, and the median daily AQI was 36. That median is higher 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 ozone on 271 days. Across the years with fuller monitoring, the share of Good days rose: an average of 82% in 2004–2006 versus 89% in 2023–2025.

Years with fewer than 120 monitored days (2003) 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%2003: Good 77 of 104 days2003: Moderate 27 of 104 days20032004: Good 281 of 363 days2004: Moderate 82 of 363 days2005: Good 301 of 352 days2005: Moderate 51 of 352 days20052006: Good 305 of 365 days2006: Moderate 53 of 365 days2006: Unhealthy for Sensitive Groups 6 of 365 days2006: Unhealthy 1 of 365 days2007: Good 310 of 365 days2007: Moderate 55 of 365 days20072008: Good 314 of 366 days2008: Moderate 52 of 366 days2009: Good 332 of 361 days2009: Moderate 29 of 361 days20092010: Good 336 of 365 days2010: Moderate 29 of 365 days2011: Good 320 of 363 days2011: Moderate 43 of 363 days20112012: Good 297 of 344 days2012: Moderate 47 of 344 days2013: Good 283 of 340 days2013: Moderate 57 of 340 days20132014: Good 315 of 347 days2014: Moderate 32 of 347 days2015: Good 342 of 362 days2015: Moderate 19 of 362 days2015: Unhealthy for Sensitive Groups 1 of 362 days20152016: Good 318 of 334 days2016: Moderate 16 of 334 days2017: Good 249 of 333 days2017: Moderate 75 of 333 days2017: Unhealthy for Sensitive Groups 6 of 333 days2017: Unhealthy 3 of 333 days20172018: Good 250 of 307 days2018: Moderate 50 of 307 days2018: Unhealthy for Sensitive Groups 6 of 307 days2018: Unhealthy 1 of 307 days2019: Good 322 of 365 days2019: Moderate 43 of 365 days20192020: Good 323 of 365 days2020: Moderate 34 of 365 days2020: Unhealthy 5 of 365 days2020: Very Unhealthy 3 of 365 days2021: Good 304 of 365 days2021: Moderate 53 of 365 days2021: Unhealthy for Sensitive Groups 3 of 365 days2021: Unhealthy 5 of 365 days20212022: Good 314 of 365 days2022: Moderate 47 of 365 days2022: Unhealthy for Sensitive Groups 4 of 365 days2023: Good 319 of 365 days2023: Moderate 43 of 365 days2023: Unhealthy 2 of 365 days2023: Very Unhealthy 1 of 365 days20232024: Good 331 of 366 days2024: Moderate 35 of 366 days2025: Good 330 of 365 days2025: Moderate 35 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 year0501002003: 90th percentile AQI 582004: 90th percentile AQI 582005: 90th percentile AQI 532006: 90th percentile AQI 552007: 90th percentile AQI 552008: 90th percentile AQI 542009: 90th percentile AQI 482010: 90th percentile AQI 482011: 90th percentile AQI 522012: 90th percentile AQI 522013: 90th percentile AQI 542014: 90th percentile AQI 492015: 90th percentile AQI 432016: 90th percentile AQI 412017: 90th percentile AQI 592018: 90th percentile AQI 592019: 90th percentile AQI 532020: 90th percentile AQI 522021: 90th percentile AQI 582022: 90th percentile AQI 542023: 90th percentile AQI 522024: 90th percentile AQI 502025: 90th percentile AQI 502003: Median AQI 362004: Median AQI 332005: Median AQI 272006: Median AQI 282007: Median AQI 262008: Median AQI 262009: Median AQI 272010: Median AQI 242011: Median AQI 232012: Median AQI 242013: Median AQI 282014: Median AQI 222015: Median AQI 192016: Median AQI 202017: Median AQI 282018: Median AQI 222019: Median AQI 222020: Median AQI 232021: Median AQI 392022: Median AQI 372023: Median AQI 392024: Median AQI 362025: Median AQI 36200320052007200920112013201520172019202120232025
  • 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
Ozone27174%
Fine particles (PM2.5)9426%

Year-by-year data

Annual AQI summary by year
YearDays with AQIGoodModerateUnhealthy for Sensitive GroupsUnhealthyVery UnhealthyHazardousMedian AQI90th pct.Max AQIMain pollutant
2025365330350000365094Ozone
2024366331350000365090Ozone
20233653194302103952259Ozone
20223653144740003754135Ozone
20213653045335003958172Ozone
20203653233405302352258PM2.5
2019365322430000225372PM2.5
20183072505061002259192PM2.5
20173332497563002859184PM2.5
2016334318160000204160PM2.5
20153623421910001943104PM2.5
2014347315320000224975PM2.5
2013340283570000285483PM2.5
2012344297470000245275PM2.5
2011363320430000235271PM2.5
2010365336290000244867PM2.5
2009361332290000274863PM2.5
2008366314520000265472PM2.5
2007365310550000265578PM2.5
20063653055361002855154PM2.5
2005352301510000275381PM2.5
2004363281820000335897PM2.5
200310477270000365874PM2.5

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 2003–2025 (EPA download page). EPA file dates: 2026-06-26. Imported into EnviroNearby November 5, 2026. How we use this data · Report a problem