Median AQI
27
Good
Washington · County air quality · 2025
Stevens County, Washington
Median AQI 27 (Good). 81.1% of monitored days rated Good, direct from EPA Air Quality System stations.
- 27
- Median AQI
- 81.1%
- Good-air days
- 0
- Unhealthy days
- 55%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Stevens County's air is good on balance, cleaner than the median US county, a median AQI of 27 with 81.1% of 243 monitored days in the Good band, driven mainly by PM2.5.
- 27
- median AQI · Good
- 81.1%
- days rated Good
- PM2.5
- main pollutant
- 55%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 119.
Data updated July 2026
- Good · 197 d · 81.1%
- Moderate · 45 d · 18.5%
- USG · 1 d · 0.4%
How did Stevens County's air break down in 2025?
Across 243 monitored days, 197 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 119 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 243 days monitored. Median AQI: 27 (Good).
Insights: Stevens County, Washington. EPA monitors recorded a median Air Quality Index of 27 across 243 measured days in 2025, earning a Good classification and a Good health grade. Of those days, 197 (81%) fell in the Good band (AQI 0–50), 45 (19%) registered Moderate readings, and 1 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 57, while the worst single-day peak hit 119 (USG). Residents averaged about 24.3 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (221 days), PM10 (22 days). Across the 2020–2025 trend window, good days shifted by -22 and the median AQI moved -15 points, placing the multi-year trajectory at improving. The worst single reading over the 2020–2025 window was AQI 119, usg but never Unhealthy. Nearby counties show comparable readings: Adams (94.7% good, AQI 19); Asotin (73.8% good, AQI 35); Benton (88.9% good, AQI 35); Chelan (87.2% good, AQI 27); Clallam (88.5% good, AQI 26); Clark (89.3% good, AQI 31).
Air Quality Summary
Good Days
81.1%
197 of 243 monitored days
6.1pp vs 75% target
Max AQI Recorded
119
USG
Health Grade
Good
90th-pct AQI 57
Stevens County, Good days share 81.1%
National avg
Share of monitored days at AQI 0-50 (Good band).
Stevens 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 243 monitored days across EPA AQI categories.
Good
197
81%
Moderate
45
19%
USG
1
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 Stevens County.
- PM2.5 · 221 days · 90.9%
- PM10 · 22 days · 9.1%
Health Impact Assessment
Good
Stevens County's air quality is rated Good based on 81.1% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 81.1% of monitored days in 2025, with a median AQI of 27. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM2.5, driving AQI on 221 of 243 monitored days.
5-Year Air Quality Trend
Air quality is improving in Stevens County. Best year: 2024 (257 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 219 | 138 | 1 | 2 | 42 | 957 |
| 2021 | 203 | 146 | 6 | 8 | 44 | 223 |
| 2022 | 208 | 149 | 7 | 1 | 43 | 153 |
| 2023 | 204 | 153 | 4 | 2 | 46 | 271 |
| 2024 | 257 | 109 | 0 | 0 | 34 | 98 |
| 2025 | 197 | 45 | 1 | 0 | 27 | 119 |
How does Stevens County compare?
How Stevens County compares
Good-day share better than US avg
Stevens County 81.1%
Adams County, Washington 94.7%
US average 76.5%
Median AQI better than US avg
Stevens County 27
Adams County, Washington 19
US average 38
Unhealthy days / yr about average
Stevens County 0
Adams County, Washington 0
US average 0
Other Counties in Washington
Air quality comparison for nearby counties in Washington.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Stevens County.
Chelan County, Washington
AQI 27 · 87.2% good
Clackamas County, Oregon
AQI 27 · 93.9% good
Silver Bow County, Montana
AQI 27 · 82.9% good
Clallam County, Washington
AQI 26 · 88.5% good
Delta County, Colorado
AQI 28 · 88.0% good
Ford County, Kansas
AQI 26 · 89.4% good
What Stevens 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 27 means for exposure. Health guidance
- See how Stevens County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Stevens County with its Washington neighbours before drawing a conclusion about the region. All of Washington
Based on 243 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 Stevens County, Washington? ▼
Stevens County has a median Air Quality Index (AQI) of 27, rated "Good." 81.1% of monitored days (197 out of 243) had good air quality in 2025.
What is the main pollutant in Stevens County? ▼
The primary pollutant in Stevens County is Fine Particles (PM2.5), which was the main AQI driver on 221 days (91% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Stevens County have? ▼
In 2025, Stevens County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 119.
Is the air quality in Stevens County getting better or worse? ▼
Air quality in Stevens County is improving based on 5-year trends (2020-2025). Best year: 2024 with 257 good days. Worst year: 2025 with 197 good days.
What does AQI 27 mean for health? ▼
Stevens County's median AQI of 27 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 Stevens County compare to other counties in Washington? ▼
Stevens County has 81.1% good air days. Nearby counties in Washington: Adams (94.7% good), Asotin (73.8% good), Benton (88.9% good), Chelan (87.2% good), Clallam (88.5% good), Clark (89.3% good).
What is the 90th percentile AQI in Stevens County? ▼
The 90th percentile AQI for Stevens County is 57, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 119 (USG).
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.