Median AQI
48
Good
Wyoming · County air quality · 2025
Fremont County, Wyoming
Median AQI 48 (Good). 61.3% of monitored days rated Good, direct from EPA Air Quality System stations.
- 48
- Median AQI
- 61.3%
- Good-air days
- 0
- Unhealthy days
- 17%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Fremont County's air is good on balance, among the more polluted 10% of US counties, a median AQI of 48 with 61.3% of 212 monitored days in the Good band, driven mainly by Ozone.
- 48
- median AQI · Good
- 61.3%
- days rated Good
- Ozone
- main pollutant
- 17%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 100.
Data updated July 2026
- Good · 130 d · 61.3%
- Moderate · 82 d · 38.7%
How did Fremont County's air break down in 2025?
Across 212 monitored days, 130 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 100 (Moderate).
EPA AQS →Air quality data from EPA Air Quality System (2025). 212 days monitored. Median AQI: 48 (Good).
Insights: Fremont County, Wyoming. EPA monitors recorded a median Air Quality Index of 48 across 212 measured days in 2025, earning a Good classification and a Moderate health grade. Of those days, 130 (61%) fell in the Good band (AQI 0–50), 82 (39%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 66, while the worst single-day peak hit 100 (Moderate). Residents averaged about 18.4 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (149 days), PM2.5 (63 days). Across the 2020–2025 trend window, good days shifted by -152 and the median AQI moved +3 points, placing the multi-year trajectory at worsening. The worst single reading over the 2020–2025 window was AQI 100, 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); Johnson (90.6% good, AQI 42); Laramie (69.8% good, AQI 47).
Air Quality Summary
Good Days
61.3%
130 of 212 monitored days
-13.7pp vs 75% target
Max AQI Recorded
100
Moderate
Health Grade
Moderate
90th-pct AQI 66
Fremont County, Good days share 61.3%
National avg
Share of monitored days at AQI 0-50 (Good band).
Fremont 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 212 monitored days across EPA AQI categories.
Good
130
61%
Moderate
82
39%
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 Fremont County.
- Ozone · 149 days · 70.3%
- PM2.5 · 63 days · 29.7%
Health Impact Assessment
Moderate
Fremont County's air quality is rated Moderate based on 61.3% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 61.3% of monitored days in 2025, with a median AQI of 48. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 149 of 212 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Fremont County. Best year: 2020 (282 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 282 | 78 | 5 | 1 | 45 | 161 |
| 2021 | 240 | 117 | 8 | 0 | 46 | 141 |
| 2022 | 254 | 111 | 0 | 0 | 46 | 100 |
| 2023 | 215 | 147 | 3 | 0 | 49 | 110 |
| 2024 | 210 | 151 | 5 | 0 | 49 | 139 |
| 2025 | 130 | 82 | 0 | 0 | 48 | 100 |
How does Fremont County compare?
How Fremont County compares
Good-day share worse than US avg
Fremont County 61.3%
Albany County, Wyoming 51.9%
US average 76.5%
Median AQI worse than US avg
Fremont County 48
Albany County, Wyoming 50
US average 38
Unhealthy days / yr about average
Fremont 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 Fremont County.
Black Hawk County, Iowa
AQI 48 · 56.6% good
Box Elder County, Utah
AQI 48 · 60.0% good
Brookings County, South Dakota
AQI 48 · 53.0% good
Clear Creek County, Colorado
AQI 48 · 64.4% good
Coconino County, Arizona
AQI 48 · 62.5% good
Columbia County, Florida
AQI 48 · 56.4% good
What Fremont County's air means for you
The air here stays in the breathable range year-round, with Ozone the main thing to watch.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-Ozone days, the guide explains what a median of 48 means for exposure. Health guidance
- See how Fremont County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Fremont County with its Wyoming neighbours before drawing a conclusion about the region. All of Wyoming
Based on 212 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 Fremont County, Wyoming? ▼
Fremont County has a median Air Quality Index (AQI) of 48, rated "Good." 61.3% of monitored days (130 out of 212) had good air quality in 2025.
What is the main pollutant in Fremont County? ▼
The primary pollutant in Fremont County is Ozone (O3), which was the main AQI driver on 149 days (70% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Fremont County have? ▼
In 2025, Fremont County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 100.
Is the air quality in Fremont County getting better or worse? ▼
Air quality in Fremont County is worsening based on 5-year trends (2020-2025). Best year: 2020 with 282 good days. Worst year: 2025 with 130 good days.
What does AQI 48 mean for health? ▼
Fremont County's median AQI of 48 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 Fremont County compare to other counties in Wyoming? ▼
Fremont County has 61.3% good air days. Nearby counties in Wyoming: Albany (51.9% good), Campbell (77.3% good), Carbon (100.0% good), Converse (94.5% good), Johnson (90.6% good), Laramie (69.8% good).
What is the 90th percentile AQI in Fremont County? ▼
The 90th percentile AQI for Fremont County is 66, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 100 (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.