Wyoming · County air quality · 2024
Big Horn County, Wyoming
Median AQI 39 (Good). 89.2% of monitored days rated Good, direct from EPA Air Quality System stations.
- 39
- Median AQI
- 89.2%
- Good-air days
- 0
- Unhealthy days
- 73%
- Cleaner than US counties
Big Horn County's 2024 annual median AQI is 39 (Good), with 89.2% Good days
According to the U.S. EPA Air Quality System, Big Horn County, Wyoming posted a 2024 median AQI of 39 (Good) across 353 monitored days, with 89.2% rated Good and 0 unhealthy or worse. This is an annual comparison, not today's advisory.
Data source EPA Air Quality System (AQS)
- Cleaner than US
- Big Horn County's 89.2% Good-day share places it cleaner than 73% of US counties in 2024.
- Closest median-AQI peer
- Chattooga County (96.3% Good, median AQI 39) is the closest nationwide median-AQI peer to Big Horn County.
- 2020–2024 trend
- Big Horn County's floor-qualifying Good-day share is worsening from 2020 to 2024 (97.2% → 89.2%).
- Median AQI
- Median AQI: 39
According to the 2024 EPA AQS county release on PlainAirData, Big Horn County, Wyoming ranks #5 of 15 by median AQI (39) and #4 by good-day share (89.2%). San Mateo County, California is #1 of 15 by median AQI (27, 88.1% Good days) at good-day-share #5 ≠ Chattooga County, Georgia #1 by good-day share (96.3%, median AQI 39) at median-AQI #5.
Annual release change
What changed in the 2024 EPA annual release
- Big Horn County's peak single-day AQI rose from 77 to 119 between the 2023 and 2024 EPA annual releases, a change of +42 points.
- Big Horn County's Good-day share fell from 93.3% to 89.2% between the 2023 and 2024 EPA annual releases, a change of -4.1 percentage points.
Data updated August 2026
- Good · 315 d · 89.2%
- Moderate · 36 d · 10.2%
- USG · 2 d · 0.6%
How did Big Horn County's air break down in 2024?
Across 353 monitored days, 315 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 119 (USG).
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 Big Horn County sits nationally
COUNT-derived placement among 951 US counties with at least 100 monitored days in 2024. Big Horn County's Good-day share is 89.2% - cleaner than 73% of that comparison set.
Big Horn County Good-day share vs. every US county
Share of monitored days in the Good band (AQI 0–50) - EPA AQS annual release
89.2% Cleaner than 73% higher than 73% 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) · 2024
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Big Horn County.
- Ozone · 353 days · 100.0%
2024 daily-monitor rhythm in Big Horn County
Month-by-month median AQI from EPA day-level county monitors (353 reported days in 2024). Jul posted the highest typical readings (median AQI 54, peak 119); Jan was cleanest at median 26. Summer months (Jun–Aug) averaged median AQI 48 vs 29 in Dec–Feb.
Five-year seasonal record
EPA day-level county files · 2020–20241,797 daily readings show a recurring local pattern: Jul has the highest matched-month median AQI (50), while Dec is lowest (26). 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
Big Horn County's air quality is rated Good based on 89.2% good air days. No unhealthy air days were recorded in 2024.
Air quality was acceptable on 89.2% of monitored days in 2024, with a median AQI of 39. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is Ozone, driving AQI on 353 of 353 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Big Horn County. Highest Good-day share: 2022 (98.3%, 356 of 362 monitored days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 349 | 8 | 2 | 0 | 38 | 126 |
| 2021 | 324 | 39 | 1 | 0 | 39 | 101 |
| 2022 | 356 | 6 | 0 | 0 | 38 | 64 |
| 2023 | 335 | 24 | 0 | 0 | 39 | 77 |
| 2024 | 315 | 36 | 2 | 0 | 39 | 119 |
How does Big Horn County compare?
How Big Horn 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 Big Horn County, Wyoming · 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.