Median AQI
34
Good
Oregon · County air quality · 2025
Grant County, Oregon
Median AQI 34 (Good). 66.7% of monitored days rated Good, direct from EPA Air Quality System stations.
- 34
- Median AQI
- 66.7%
- Good-air days
- 0
- Unhealthy days
- 25%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Grant County's air is good on balance, more polluted than the median US county, a median AQI of 34 with 66.7% of 180 monitored days in the Good band, driven mainly by PM2.5.
- 34
- median AQI · Good
- 66.7%
- days rated Good
- PM2.5
- main pollutant
- 25%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 86.
Data updated July 2026
- Good · 120 d · 66.7%
- Moderate · 60 d · 33.3%
How did Grant County's air break down in 2025?
Across 180 monitored days, 120 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 86 (Moderate).
EPA AQS →Air quality data from EPA Air Quality System (2025). 180 days monitored. Median AQI: 34 (Good).
Insights: Grant County, Oregon. EPA monitors recorded a median Air Quality Index of 34 across 180 measured days in 2025, earning a Good classification and a Moderate health grade. Of those days, 120 (67%) fell in the Good band (AQI 0–50), 60 (33%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 69, while the worst single-day peak hit 86 (Moderate). Residents averaged about 20.0 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (180 days). Across the 2020–2025 trend window, good days shifted by -76 and the median AQI moved -10 points, placing the multi-year trajectory at improving. The worst single reading over the 2020–2025 window was AQI 86, moderate but never Unhealthy. Nearby counties show comparable readings: Baker (89.0% good, AQI 25); Clackamas (93.9% good, AQI 27); Columbia (96.7% good, AQI 25); Crook (80.7% good, AQI 24); Deschutes (93.4% good, AQI 22); Harney (70.7% good, AQI 26).
Air Quality Summary
Good Days
66.7%
120 of 180 monitored days
-8.3pp vs 75% target
Max AQI Recorded
86
Moderate
Health Grade
Moderate
90th-pct AQI 69
Grant County, Good days share 66.7%
National avg
Share of monitored days at AQI 0-50 (Good band).
Grant 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 180 monitored days across EPA AQI categories.
Good
120
67%
Moderate
60
33%
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 Grant County.
- PM2.5 · 180 days · 100.0%
Health Impact Assessment
Moderate
Grant County's air quality is rated Moderate based on 66.7% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 66.7% of monitored days in 2025, with a median AQI of 34. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM2.5, driving AQI on 180 of 180 monitored days.
5-Year Air Quality Trend
Air quality is improving in Grant County. Best year: 2023 (207 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 196 | 161 | 1 | 5 | 44 | 393 |
| 2021 | 178 | 177 | 5 | 5 | 51 | 175 |
| 2022 | 198 | 166 | 1 | 0 | 46 | 108 |
| 2023 | 207 | 156 | 2 | 0 | 44 | 110 |
| 2024 | 189 | 158 | 5 | 13 | 49 | 204 |
| 2025 | 120 | 60 | 0 | 0 | 34 | 86 |
How does Grant County compare?
How Grant County compares
Good-day share worse than US avg
Grant County 66.7%
Baker County, Oregon 89.0%
US average 76.5%
Median AQI better than US avg
Grant County 34
Baker County, Oregon 25
US average 38
Unhealthy days / yr about average
Grant 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 Grant County.
Belknap County, New Hampshire
AQI 34 · 87.9% good
Dyer County, Tennessee
AQI 34 · 79.4% good
Flagler County, Florida
AQI 34 · 97.4% good
Highlands County, Florida
AQI 34 · 93.2% good
Johnson County, Texas
AQI 34 · 91.6% good
Knox County, Maine
AQI 34 · 97.3% good
What Grant 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 34 means for exposure. Health guidance
- See how Grant County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Grant County with its Oregon neighbours before drawing a conclusion about the region. All of Oregon
Based on 180 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 Grant County, Oregon? ▼
Grant County has a median Air Quality Index (AQI) of 34, rated "Good." 66.7% of monitored days (120 out of 180) had good air quality in 2025.
What is the main pollutant in Grant County? ▼
The primary pollutant in Grant County is Fine Particles (PM2.5), which was the main AQI driver on 180 days (100% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Grant County have? ▼
In 2025, Grant County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 86.
Is the air quality in Grant County getting better or worse? ▼
Air quality in Grant County is improving based on 5-year trends (2020-2025). Best year: 2023 with 207 good days. Worst year: 2025 with 120 good days.
What does AQI 34 mean for health? ▼
Grant County's median AQI of 34 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 Grant County compare to other counties in Oregon? ▼
Grant County has 66.7% good air days. Nearby counties in Oregon: Baker (89.0% good), Clackamas (93.9% good), Columbia (96.7% good), Crook (80.7% good), Deschutes (93.4% good), Harney (70.7% good).
What is the 90th percentile AQI in Grant County? ▼
The 90th percentile AQI for Grant County is 69, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 86 (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.