Median AQI
25
Good
Oregon · County air quality · 2025
Columbia County, Oregon
Median AQI 25 (Good). 96.7% of monitored days rated Good, direct from EPA Air Quality System stations.
- 25
- Median AQI
- 96.7%
- Good-air days
- 0
- Unhealthy days
- 93%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Columbia County's air is good on balance, among the cleanest 10% of US counties, a median AQI of 25 with 96.7% of 181 monitored days in the Good band, driven mainly by PM2.5.
- 25
- median AQI · Good
- 96.7%
- days rated Good
- PM2.5
- main pollutant
- 93%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 69.
Data updated July 2026
- Good · 175 d · 96.7%
- Moderate · 6 d · 3.3%
How did Columbia County's air break down in 2025?
Across 181 monitored days, 175 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 69 (Moderate).
EPA AQS →Air quality data from EPA Air Quality System (2025). 181 days monitored. Median AQI: 25 (Good).
Insights: Columbia County, Oregon. EPA monitors recorded a median Air Quality Index of 25 across 181 measured days in 2025, earning a Good classification and a Excellent health grade. Of those days, 175 (97%) fell in the Good band (AQI 0–50), 6 (3%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 40, while the worst single-day peak hit 69 (Moderate). Residents averaged about 29.0 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (134 days), Ozone (47 days). Across the 2020–2025 trend window, good days shifted by -157 and the median AQI moved -3 points, placing the multi-year trajectory at improving. The worst single reading over the 2020–2025 window was AQI 69, moderate but never Unhealthy. Nearby counties show comparable readings: Baker (89.0% good, AQI 25); Clackamas (93.9% good, AQI 27); Crook (80.7% good, AQI 24); Deschutes (93.4% good, AQI 22); Grant (66.7% good, AQI 34); Harney (70.7% good, AQI 26).
Air Quality Summary
Good Days
96.7%
175 of 181 monitored days
21.7pp vs 75% target
Max AQI Recorded
69
Moderate
Health Grade
Excellent
90th-pct AQI 40
Columbia County, Good days share 96.7%
National avg
Share of monitored days at AQI 0-50 (Good band).
Columbia County, Unhealthy-or-worse share 0.0%
National avg
Share of monitored days above AQI 150 (Unhealthy or worse). Bar maxes at 10% (worst-county ceiling).
AQI Day Breakdown (2025)
Distribution of 181 monitored days across EPA AQI categories.
Good
175
97%
Moderate
6
3%
USG
0
0%
Unhealthy
0
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Columbia County.
- PM2.5 · 134 days · 74.0%
- Ozone · 47 days · 26.0%
Health Impact Assessment
Excellent
Columbia County's air quality is rated Excellent based on 96.7% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 96.7% of monitored days in 2025, with a median AQI of 25. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM2.5, driving AQI on 134 of 181 monitored days.
5-Year Air Quality Trend
Air quality is improving in Columbia County. Best year: 2024 (354 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 332 | 22 | 1 | 2 | 28 | 293 |
| 2021 | 319 | 26 | 0 | 0 | 29 | 66 |
| 2022 | 293 | 66 | 1 | 2 | 31 | 162 |
| 2023 | 329 | 34 | 2 | 0 | 29 | 115 |
| 2024 | 354 | 10 | 0 | 0 | 26 | 74 |
| 2025 | 175 | 6 | 0 | 0 | 25 | 69 |
How does Columbia County compare?
How Columbia County compares
Good-day share better than US avg
Columbia County 96.7%
Baker County, Oregon 89.0%
US average 76.5%
Median AQI better than US avg
Columbia County 25
Baker County, Oregon 25
US average 38
Unhealthy days / yr about average
Columbia County 0
Baker County, Oregon 0
US average 0
Other Counties in Oregon
Air quality comparison for nearby counties in Oregon.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Columbia County.
Baker County, Oregon
AQI 25 · 89.0% good
Brown County, South Dakota
AQI 25 · 87.1% good
Fremont County, Colorado
AQI 25 · 91.1% good
Lubbock County, Texas
AQI 25 · 89.9% good
Sherman County, Kansas
AQI 25 · 86.6% good
Walla Walla County, Washington
AQI 25 · 86.0% good
What Columbia County's air means for you
The air here stays in the breathable range year-round, with PM2.5 the main thing to watch.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-PM2.5 days, the guide explains what a median of 25 means for exposure. Health guidance
- See how Columbia County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Columbia County with its Oregon neighbours before drawing a conclusion about the region. All of Oregon
Based on 181 EPA-monitored days in 2025; figures reflect only days the monitors reported. Source: EPA Air Quality System annual summaries.
More Air Quality Data
Air Quality Guides
Frequently Asked Questions
What is the air quality in Columbia County, Oregon? ▼
Columbia County has a median Air Quality Index (AQI) of 25, rated "Good." 96.7% of monitored days (175 out of 181) had good air quality in 2025.
What is the main pollutant in Columbia County? ▼
The primary pollutant in Columbia County is Fine Particles (PM2.5), which was the main AQI driver on 134 days (74% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Columbia County have? ▼
In 2025, Columbia County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 69.
Is the air quality in Columbia County getting better or worse? ▼
Air quality in Columbia County is improving based on 5-year trends (2020-2025). Best year: 2024 with 354 good days. Worst year: 2025 with 175 good days.
What does AQI 25 mean for health? ▼
Columbia County's median AQI of 25 falls in the "Good" category. See the <a href="/guides/understanding-aqi" class="underline">AQI category guide</a> for what each range means for health.
How does Columbia County compare to other counties in Oregon? ▼
Columbia County has 96.7% good air days. Nearby counties in Oregon: Baker (89.0% good), Clackamas (93.9% good), Crook (80.7% good), Deschutes (93.4% good), Grant (66.7% good), Harney (70.7% good).
What is the 90th percentile AQI in Columbia County? ▼
The 90th percentile AQI for Columbia County is 40, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 69 (Moderate).
Data Sources
Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by County dataset, 2020–2025 (aqs.epa.gov). For current conditions (not shown here — this page is historical annual data), see EPA AirNow (airnow.gov). See our methodology for how AQI, median, and coverage figures are computed.
Informational only, not professional advice. Data from EPA AQS. See our disclaimer.
Every figure on PlainAir is rendered directly from EPA AQS air-quality monitoring data, no number is typed in by an editor. This page draws directly on EPA AQS air-quality monitoring data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.