Oklahoma · County air quality · 2025
Dewey County, Oklahoma
Median AQI 46 (Good). 63.7% of monitored days rated Good, direct from EPA Air Quality System stations.
- 46
- Median AQI
- 63.7%
- Good-air days
- 1
- Unhealthy days
- 21%
- Cleaner than US counties
Dewey County's 2025 annual median AQI is 46 (Good), with 63.7% Good days
According to the U.S. EPA Air Quality System, Dewey County, Oklahoma posted a 2025 median AQI of 46 (Good) across 364 monitored days, with 63.7% rated Good and 1 unhealthy or worse. This is an annual comparison, not today's advisory.
Data source EPA Air Quality System (AQS)
- Cleaner than US
- Dewey County's 63.7% Good-day share places it cleaner than 21% of US counties in 2025.
- Closest median-AQI peer
- Beaver County (55.6% Good, median AQI 46) is the closest nationwide median-AQI peer to Dewey County.
- 2020–2025 trend
- Dewey County's floor-qualifying Good-day share is worsening from 2020 to 2025 (72.9% → 63.7%).
- Median AQI
- Median AQI: 46
According to the 2025 EPA AQS county release on PlainAirData, Dewey County, Oklahoma ranks #787 of 951 by median AQI (46) and #756 by good-day share (63.7%). Ponce County, Puerto Rico is #1 of 951 by median AQI (3, 91.4% Good days) at good-day-share #159 ≠ largest of 7 at 100.0% Good days #1 by good-day share (100.0%, median AQI 9) at median-AQI #7.
Annual release change
What changed in the 2025 EPA annual release
- Dewey County's peak single-day AQI rose from 112 to 164 between the 2024 and 2025 EPA annual releases, a change of +52 points.
- Dewey County's Good-day share rose from 60.4% to 63.7% between the 2024 and 2025 EPA annual releases, a change of +3.4 percentage points.
- Dewey County's Unhealthy-category days rose from 0 to 1 between the 2024 and 2025 EPA annual releases, a change of +1 days.
Data updated August 2026
- Good · 232 d · 63.7%
- Moderate · 131 d · 36.0%
- Unhealthy · 1 d · 0.3%
How did Dewey County's air break down in 2025?
Across 364 monitored days, 232 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 →Share of monitored days at AQI 0-50 (Good band).
Share of monitored days above AQI 150 (Unhealthy or worse). Bar maxes at 10% (worst-county ceiling).
Where Dewey County sits nationally
COUNT-derived placement among 951 US counties with at least 100 monitored days in 2025. Dewey County's Good-day share is 63.7% - cleaner than 21% of that comparison set.
Dewey County Good-day share vs. every US county
Share of monitored days in the Good band (AQI 0–50) - EPA AQS annual release
63.7% 21st percentile higher than 21% of 951 US counties
Each bar is a band; taller bars hold more US counties. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count, share, and where it sits relative to this entry.
Source U.S. Environmental Protection Agency, Air Quality System (AQS) · 2025
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Dewey County.
- Ozone · 210 days · 57.7%
- PM2.5 · 154 days · 42.3%
2024 daily-monitor rhythm in Dewey County
Month-by-month median AQI from EPA day-level county monitors (366 reported days in 2024). Aug posted the highest typical readings (median AQI 59, peak 105); Jan was cleanest at median 23. Summer months (Jun–Aug) averaged median AQI 57 vs 26 in Dec–Feb.
Five-year seasonal record
EPA day-level county files · 2020–20241,807 daily readings show a recurring local pattern: Jul has the highest matched-month median AQI (55), while Jan is lowest (29). Each cell is that month’s median daily AQI, not a current-air forecast.
Lower AQI is better. The colors summarize EPA AQI bands; gaps mean the county had no day-level record for that month.
Health Impact Assessment
Dewey County's air quality is rated Moderate based on 63.7% 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 210 of 364 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Dewey County. Highest Good-day share: 2020 (72.9%, 266 of 365 monitored 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 | 232 | 131 | 0 | 1 | 46 | 164 |
How does Dewey County compare?
How Dewey County compares
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. Spotted a figure that looks wrong? Report a correction.
Source: U.S. EPA Air Quality System (AQS) Annual AQI by county summary files for Dewey County, Oklahoma · 2020–2025
Download this county's annual AQI row as CSV , with the same EPA fields and denominator shown on this page.
Every figure on PlainAirData 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.