Median AQI
44
Good
Oklahoma · County air quality · 2025
Washington County, Oklahoma
Median AQI 44 (Good). 65.6% of monitored days rated Good, direct from EPA Air Quality System stations.
- 44
- Median AQI
- 65.6%
- Good-air days
- 1
- Unhealthy days
- 23%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Washington County's air is good on balance, among the more polluted 10% of US counties, a median AQI of 44 with 65.6% of 273 monitored days in the Good band, driven mainly by Ozone.
- 44
- median AQI · Good
- 65.6%
- days rated Good
- Ozone
- main pollutant
- 23%
- cleaner than US counties
1 day reached Unhealthy or worse; the worst single reading hit AQI 168.
Data updated July 2026
- Good · 179 d · 65.6%
- Moderate · 92 d · 33.7%
- USG · 1 d · 0.4%
- Unhealthy · 1 d · 0.4%
How did Washington County's air break down in 2025?
Across 273 monitored days, 179 fell in the Good band (AQI 0–50) and 1 reached Unhealthy or worse. The worst single day peaked at AQI 168 (Unhealthy).
EPA AQS →Air quality data from EPA Air Quality System (2025). 273 days monitored. Median AQI: 44 (Good).
Insights: Washington County, Oklahoma. EPA monitors recorded a median Air Quality Index of 44 across 273 measured days in 2025, earning a Good classification and a Moderate health grade. Of those days, 179 (66%) fell in the Good band (AQI 0–50), 92 (34%) registered Moderate readings, and 1 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 62, while the worst single-day peak hit 168 (Unhealthy). Residents averaged about 19.7 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (160 days), PM2.5 (113 days). Across the 2020–2025 trend window, good days shifted by -53 and the median AQI moved +1 points, placing the multi-year trajectory at stable. Residents and visitors experienced 1 unhealthy-or-worse days combined, periods when the EPA recommends sensitive groups limit prolonged outdoor exertion. Nearby counties show comparable readings: Adair (59.2% good, AQI 45); Canadian (78.0% good, AQI 44); Carter (80.9% good, AQI 33); Cleveland (53.7% good, AQI 49); Comanche (63.8% good, AQI 45); Creek (80.1% good, AQI 43).
Air Quality Summary
Good Days
65.6%
179 of 273 monitored days
-9.4pp vs 75% target
Max AQI Recorded
168
Unhealthy
Health Grade
Moderate
90th-pct AQI 62
Washington County, Good days share 65.6%
National avg
Share of monitored days at AQI 0-50 (Good band).
Washington County, Unhealthy-or-worse share 0.4%
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 273 monitored days across EPA AQI categories.
Good
179
66%
Moderate
92
34%
USG
1
0%
Unhealthy
1
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Washington County.
- Ozone · 160 days · 58.6%
- PM2.5 · 113 days · 41.4%
Health Impact Assessment
Moderate
Washington County's air quality is rated Moderate based on 65.6% good air days. There were 1 unhealthy days in 2025 when outdoor activity should be limited.
Air quality is acceptable most days, but 1 days reached "Unhealthy for Sensitive Groups" (AQI 101-150) and peak AQI reached 168. Sensitive groups should monitor real-time conditions at AirNow.gov.
The dominant pollutant is Ozone, driving AQI on 160 of 273 monitored days.
5-Year Air Quality Trend
Air quality is stable in Washington County. Best year: 2020 (232 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 232 | 111 | 1 | 0 | 43 | 101 |
| 2021 | 168 | 170 | 7 | 0 | 51 | 139 |
| 2024 | 182 | 128 | 7 | 1 | 47 | 156 |
| 2025 | 179 | 92 | 1 | 1 | 44 | 168 |
How does Washington County compare?
How Washington County compares
Good-day share worse than US avg
Washington County 65.6%
Adair County, Oklahoma 59.2%
US average 76.5%
Median AQI worse than US avg
Washington County 44
Adair County, Oklahoma 45
US average 38
Unhealthy days / yr worse than US avg
Washington County 1
Adair County, Oklahoma 2
US average 0
Other Counties in Oklahoma
Air quality comparison for nearby counties in Oklahoma.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Washington County.
Baltimore County, Maryland
AQI 44 · 70.4% good
Baltimore (City) County, Maryland
AQI 44 · 68.7% good
Bartholomew County, Indiana
AQI 44 · 69.2% good
Berks County, Pennsylvania
AQI 44 · 65.6% good
Bolivar County, Mississippi
AQI 44 · 70.3% good
Brewster County, Texas
AQI 44 · 69.0% good
What Washington County's air means for you
On most days the air here is fine, but Ozone drives 1 unhealthy-or-worse day a year that sensitive groups should plan around.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-Ozone days, the guide explains what a median of 44 means for exposure. Health guidance
- See how Washington County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Washington County with its Oklahoma neighbours before drawing a conclusion about the region. All of Oklahoma
Based on 273 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 Washington County, Oklahoma? ▼
Washington County has a median Air Quality Index (AQI) of 44, rated "Good." 65.6% of monitored days (179 out of 273) had good air quality in 2025.
What is the main pollutant in Washington County? ▼
The primary pollutant in Washington County is Ozone (O3), which was the main AQI driver on 160 days (59% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Washington County have? ▼
In 2025, Washington County recorded 1 unhealthy air days (1 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 168.
Is the air quality in Washington County getting better or worse? ▼
Air quality in Washington County is stable based on 5-year trends (2020-2025). Best year: 2020 with 232 good days. Worst year: 2021 with 168 good days.
What does AQI 44 mean for health? ▼
Washington County's median AQI of 44 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 Washington County compare to other counties in Oklahoma? ▼
Washington County has 65.6% good air days. Nearby counties in Oklahoma: Adair (59.2% good), Canadian (78.0% good), Carter (80.9% good), Cleveland (53.7% good), Comanche (63.8% good), Creek (80.1% good).
What is the 90th percentile AQI in Washington County? ▼
The 90th percentile AQI for Washington County is 62, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 168 (Unhealthy).
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.