Median AQI
33
Good
Wyoming · County air quality · 2025
Sheridan County, Wyoming
Median AQI 33 (Good). 84.6% of monitored days rated Good, direct from EPA Air Quality System stations.
- 33
- Median AQI
- 84.6%
- Good-air days
- 0
- Unhealthy days
- 64%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Sheridan County's air is good on balance, cleaner than the median US county, a median AQI of 33 with 84.6% of 175 monitored days in the Good band, driven mainly by PM2.5.
- 33
- median AQI · Good
- 84.6%
- days rated Good
- PM2.5
- main pollutant
- 64%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 70.
Data updated July 2026
- Good · 148 d · 84.6%
- Moderate · 27 d · 15.4%
How did Sheridan County's air break down in 2025?
Across 175 monitored days, 148 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 70 (Moderate).
EPA AQS →Air quality data from EPA Air Quality System (2025). 175 days monitored. Median AQI: 33 (Good).
Insights: Sheridan County, Wyoming. EPA monitors recorded a median Air Quality Index of 33 across 175 measured days in 2025, earning a Good classification and a Good health grade. Of those days, 148 (85%) fell in the Good band (AQI 0–50), 27 (15%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 53, while the worst single-day peak hit 70 (Moderate). Residents averaged about 25.4 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (123 days), Ozone (47 days), NO2 (3 days), PM10 (2 days). Across the 2020–2025 trend window, good days shifted by -186 and the median AQI moved -7 points, placing the multi-year trajectory at worsening. The worst single reading over the 2020–2025 window was AQI 70, moderate but never Unhealthy. Nearby counties show comparable readings: Albany (51.9% good, AQI 50); Campbell (77.3% good, AQI 43); Carbon (100.0% good, AQI 7); Converse (94.5% good, AQI 41); Fremont (61.3% good, AQI 48); Johnson (90.6% good, AQI 42).
Air Quality Summary
Good Days
84.6%
148 of 175 monitored days
9.6pp vs 75% target
Max AQI Recorded
70
Moderate
Health Grade
Good
90th-pct AQI 53
Sheridan County, Good days share 84.6%
National avg
Share of monitored days at AQI 0-50 (Good band).
Sheridan 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 175 monitored days across EPA AQI categories.
Good
148
85%
Moderate
27
15%
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 Sheridan County.
- PM2.5 · 123 days · 70.3%
- Ozone · 47 days · 26.9%
- NO₂ · 3 days · 1.7%
- PM10 · 2 days · 1.1%
Health Impact Assessment
Good
Sheridan County's air quality is rated Good based on 84.6% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 84.6% of monitored days in 2025, with a median AQI of 33. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM2.5, driving AQI on 123 of 175 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Sheridan County. Best year: 2020 (334 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 334 | 32 | 0 | 0 | 40 | 100 |
| 2021 | 302 | 55 | 7 | 0 | 40 | 115 |
| 2022 | 270 | 95 | 0 | 0 | 44 | 90 |
| 2023 | 283 | 79 | 2 | 1 | 43 | 175 |
| 2024 | 281 | 69 | 9 | 6 | 44 | 205 |
| 2025 | 148 | 27 | 0 | 0 | 33 | 70 |
How does Sheridan County compare?
How Sheridan County compares
Good-day share better than US avg
Sheridan County 84.6%
Albany County, Wyoming 51.9%
US average 76.5%
Median AQI better than US avg
Sheridan County 33
Albany County, Wyoming 50
US average 38
Unhealthy days / yr about average
Sheridan County 0
Albany County, Wyoming 0
US average 0
Other Counties in Wyoming
Air quality comparison for nearby counties in Wyoming.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Sheridan County.
Ascension County, Louisiana
AQI 33 · 94.1% good
Athens County, Ohio
AQI 33 · 80.3% good
Brazoria County, Texas
AQI 33 · 84.8% good
Bristol City County, Virginia
AQI 33 · 78.3% good
Carter County, Oklahoma
AQI 33 · 80.9% good
Codington County, South Dakota
AQI 33 · 82.1% good
What Sheridan 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 33 means for exposure. Health guidance
- See how Sheridan County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Sheridan County with its Wyoming neighbours before drawing a conclusion about the region. All of Wyoming
Based on 175 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 Sheridan County, Wyoming? ▼
Sheridan County has a median Air Quality Index (AQI) of 33, rated "Good." 84.6% of monitored days (148 out of 175) had good air quality in 2025.
What is the main pollutant in Sheridan County? ▼
The primary pollutant in Sheridan County is Fine Particles (PM2.5), which was the main AQI driver on 123 days (70% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Sheridan County have? ▼
In 2025, Sheridan County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 70.
Is the air quality in Sheridan County getting better or worse? ▼
Air quality in Sheridan County is worsening based on 5-year trends (2020-2025). Best year: 2020 with 334 good days. Worst year: 2025 with 148 good days.
What does AQI 33 mean for health? ▼
Sheridan County's median AQI of 33 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 Sheridan County compare to other counties in Wyoming? ▼
Sheridan County has 84.6% good air days. Nearby counties in Wyoming: Albany (51.9% good), Campbell (77.3% good), Carbon (100.0% good), Converse (94.5% good), Fremont (61.3% good), Johnson (90.6% good).
What is the 90th percentile AQI in Sheridan County? ▼
The 90th percentile AQI for Sheridan County is 53, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 70 (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.