Median AQI
20
Good
Washington · County air quality · 2025
Whitman County, Washington
Median AQI 20 (Good). 93.8% of monitored days rated Good, direct from EPA Air Quality System stations.
- 20
- Median AQI
- 93.8%
- Good-air days
- 0
- Unhealthy days
- 85%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Whitman County's air is good on balance, cleaner than most US counties, a median AQI of 20 with 93.8% of 243 monitored days in the Good band, driven mainly by PM2.5.
- 20
- median AQI · Good
- 93.8%
- days rated Good
- PM2.5
- main pollutant
- 85%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 97.
Data updated July 2026
- Good · 228 d · 93.8%
- Moderate · 15 d · 6.2%
How did Whitman County's air break down in 2025?
Across 243 monitored days, 228 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 97 (Moderate).
EPA AQS →Air quality data from EPA Air Quality System (2025). 243 days monitored. Median AQI: 20 (Good).
Insights: Whitman County, Washington. EPA monitors recorded a median Air Quality Index of 20 across 243 measured days in 2025, earning a Good classification and a Excellent health grade. Of those days, 228 (94%) fell in the Good band (AQI 0–50), 15 (6%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 41, while the worst single-day peak hit 97 (Moderate). Residents averaged about 28.1 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (243 days). Across the 2020–2025 trend window, good days shifted by -107 and the median AQI moved +1 points, placing the multi-year trajectory at stable. The worst single reading over the 2020–2025 window was AQI 97, moderate 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
93.8%
228 of 243 monitored days
18.8pp vs 75% target
Max AQI Recorded
97
Moderate
Health Grade
Excellent
90th-pct AQI 41
Whitman County, Good days share 93.8%
National avg
Share of monitored days at AQI 0-50 (Good band).
Whitman 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
228
94%
Moderate
15
6%
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 Whitman County.
- PM2.5 · 243 days · 100.0%
Health Impact Assessment
Excellent
Whitman County's air quality is rated Excellent based on 93.8% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 93.8% of monitored days in 2025, with a median AQI of 20. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM2.5, driving AQI on 243 of 243 monitored days.
5-Year Air Quality Trend
Air quality is stable in Whitman County. Best year: 2020 (335 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 335 | 23 | 1 | 5 | 19 | 237 |
| 2021 | 310 | 45 | 5 | 4 | 22 | 218 |
| 2022 | 306 | 55 | 0 | 4 | 24 | 190 |
| 2023 | 323 | 40 | 0 | 0 | 26 | 326 |
| 2024 | 310 | 56 | 0 | 0 | 20 | 97 |
| 2025 | 228 | 15 | 0 | 0 | 20 | 97 |
How does Whitman County compare?
How Whitman County compares
Good-day share better than US avg
Whitman County 93.8%
Adams County, Washington 94.7%
US average 76.5%
Median AQI better than US avg
Whitman County 20
Adams County, Washington 19
US average 38
Unhealthy days / yr about average
Whitman 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 Whitman County.
Cass County, Nebraska
AQI 20 · 96.5% good
Hyde County, North Carolina
AQI 20 · 100.0% good
Adams County, Washington
AQI 19 · 94.7% good
Bonneville County, Idaho
AQI 19 · 94.9% good
Cowlitz County, Washington
AQI 21 · 91.6% good
Elko County, Nevada
AQI 19 · 90.8% good
What Whitman 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 20 means for exposure. Health guidance
- See how Whitman County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Whitman 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 Whitman County, Washington? ▼
Whitman County has a median Air Quality Index (AQI) of 20, rated "Good." 93.8% of monitored days (228 out of 243) had good air quality in 2025.
What is the main pollutant in Whitman County? ▼
The primary pollutant in Whitman County is Fine Particles (PM2.5), which was the main AQI driver on 243 days (100% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Whitman County have? ▼
In 2025, Whitman County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 97.
Is the air quality in Whitman County getting better or worse? ▼
Air quality in Whitman County is stable based on 5-year trends (2020-2025). Best year: 2020 with 335 good days. Worst year: 2025 with 228 good days.
What does AQI 20 mean for health? ▼
Whitman County's median AQI of 20 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 Whitman County compare to other counties in Washington? ▼
Whitman County has 93.8% 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 Whitman County? ▼
The 90th percentile AQI for Whitman County is 41, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 97 (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.