Median AQI
49
Good
Oklahoma · County air quality · 2025
Dewey County, Oklahoma
Median AQI 49 (Good). 56.6% of monitored days rated Good, direct from EPA Air Quality System stations.
- 49
- Median AQI
- 56.6%
- Good-air days
- 1
- Unhealthy days
- 11%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Dewey County's air is good on balance, among the more polluted 10% of US counties, a median AQI of 49 with 56.6% of 272 monitored days in the Good band, driven mainly by Ozone.
- 49
- median AQI · Good
- 56.6%
- days rated Good
- Ozone
- main pollutant
- 11%
- cleaner than US counties
1 day reached Unhealthy or worse; the worst single reading hit AQI 164.
Data updated July 2026
- Good · 154 d · 56.6%
- Moderate · 117 d · 43.0%
- Unhealthy · 1 d · 0.4%
How did Dewey County's air break down in 2025?
Across 272 monitored days, 154 fell in the Good band (AQI 0–50) and 1 reached Unhealthy or worse. The worst single day peaked at AQI 164 (Unhealthy).
EPA AQS →Air quality data from EPA Air Quality System (2025). 272 days monitored. Median AQI: 49 (Good).
Insights: Dewey County, Oklahoma. EPA monitors recorded a median Air Quality Index of 49 across 272 measured days in 2025, earning a Good classification and a Moderate health grade. Of those days, 154 (57%) fell in the Good band (AQI 0–50), 117 (43%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 71, while the worst single-day peak hit 164 (Unhealthy). Residents averaged about 17.0 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (157 days), PM2.5 (115 days). Across the 2020–2025 trend window, good days shifted by -112 and the median AQI moved +6 points, placing the multi-year trajectory at worsening. 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
56.6%
154 of 272 monitored days
-18.4pp vs 75% target
Max AQI Recorded
164
Unhealthy
Health Grade
Moderate
90th-pct AQI 71
Dewey County, Good days share 56.6%
National avg
Share of monitored days at AQI 0-50 (Good band).
Dewey 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 272 monitored days across EPA AQI categories.
Good
154
57%
Moderate
117
43%
USG
0
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 Dewey County.
- Ozone · 157 days · 57.7%
- PM2.5 · 115 days · 42.3%
Health Impact Assessment
Moderate
Dewey County's air quality is rated Moderate based on 56.6% good air days. There were 1 unhealthy days in 2025 when outdoor activity should be limited.
Air quality is acceptable most days, but 0 days reached "Unhealthy for Sensitive Groups" (AQI 101-150) and peak AQI reached 164. Sensitive groups should monitor real-time conditions at AirNow.gov.
The dominant pollutant is Ozone, driving AQI on 157 of 272 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Dewey County. Best year: 2020 (266 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 266 | 99 | 0 | 0 | 43 | 99 |
| 2021 | 261 | 103 | 1 | 0 | 44 | 116 |
| 2022 | 219 | 124 | 3 | 0 | 47 | 129 |
| 2023 | 221 | 144 | 0 | 0 | 46 | 100 |
| 2024 | 221 | 139 | 6 | 0 | 47 | 112 |
| 2025 | 154 | 117 | 0 | 1 | 49 | 164 |
How does Dewey County compare?
How Dewey County compares
Good-day share worse than US avg
Dewey County 56.6%
Adair County, Oklahoma 59.2%
US average 76.5%
Median AQI worse than US avg
Dewey County 49
Adair County, Oklahoma 45
US average 38
Unhealthy days / yr worse than US avg
Dewey 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 Dewey County.
Allegheny County, Pennsylvania
AQI 49 · 51.6% good
Arkansas County, Arkansas
AQI 49 · 51.6% good
Ashley County, Arkansas
AQI 49 · 53.9% good
Clayton County, Georgia
AQI 49 · 53.1% good
Cleveland County, Oklahoma
AQI 49 · 53.7% good
Douglas County, Colorado
AQI 49 · 57.9% good
What Dewey 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 49 means for exposure. Health guidance
- See how Dewey County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Dewey County with its Oklahoma neighbours before drawing a conclusion about the region. All of Oklahoma
Based on 272 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 Dewey County, Oklahoma? ▼
Dewey County has a median Air Quality Index (AQI) of 49, rated "Good." 56.6% of monitored days (154 out of 272) had good air quality in 2025.
What is the main pollutant in Dewey County? ▼
The primary pollutant in Dewey County is Ozone (O3), which was the main AQI driver on 157 days (58% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Dewey County have? ▼
In 2025, Dewey County recorded 1 unhealthy air days (1 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 164.
Is the air quality in Dewey County getting better or worse? ▼
Air quality in Dewey County is worsening based on 5-year trends (2020-2025). Best year: 2020 with 266 good days. Worst year: 2025 with 154 good days.
What does AQI 49 mean for health? ▼
Dewey County's median AQI of 49 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 Dewey County compare to other counties in Oklahoma? ▼
Dewey County has 56.6% 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 Dewey County? ▼
The 90th percentile AQI for Dewey County is 71, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 164 (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.