Median AQI
13
Good
Montana · County air quality · 2025
Beaverhead County, Montana
Median AQI 13 (Good). 94.7% of monitored days rated Good, direct from EPA Air Quality System stations.
- 13
- Median AQI
- 94.7%
- Good-air days
- 0
- Unhealthy days
- 91%
- Cleaner than US counties
Beaverhead County's 2025 annual median AQI is 13 (Good), with 94.7% Good days
According to the U.S. EPA Air Quality System, Beaverhead County, Montana posted a 2025 median AQI of 13 (Good) across 342 monitored days, with 94.7% 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
- Beaverhead County's 94.7% Good-day share places it cleaner than 91% of US counties in 2025.
- Closest median-AQI peer
- Navajo County (99.5% Good, median AQI 13) is the closest nationwide median-AQI peer to Beaverhead County.
- 2023–2025 trend
- Beaverhead County's floor-qualifying Good-day share is stable from 2023 to 2025 (96.1% → 94.7%).
- Median AQI
- Median AQI: 13
The verdict
According to EPA Air Quality System monitoring data, Beaverhead County's air is good on balance, among the cleanest 10% of US counties, a median AQI of 13 with 94.7% of 342 monitored days in the Good band, driven mainly by PM2.5.
- 13
- median AQI · Good
- 94.7%
- days rated Good
- PM2.5
- main pollutant
- 91%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 95.
Annual release change
What changed in the 2025 EPA annual release
- Beaverhead County's Good-day share rose from 86.1% to 94.7% between the 2024 and 2025 EPA annual releases, a change of +8.6 percentage points.
- Beaverhead County's peak single-day AQI fell from 180 to 95 between the 2024 and 2025 EPA annual releases, a change of -85 points.
- Beaverhead County's Unhealthy-category days fell from 2 to 0 between the 2024 and 2025 EPA annual releases, a change of -2 days.
Data updated August 2026
- Good · 324 d · 94.7%
- Moderate · 18 d · 5.3%
How did Beaverhead County's air break down in 2025?
Across 342 monitored days, 324 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 95 (Moderate).
EPA AQS →Air quality data from EPA Air Quality System (2025). 342 days monitored. Median AQI: 13 (Good).
Insights: Beaverhead County, Montana. EPA monitors recorded a median Air Quality Index of 13 across 342 measured days in 2025, earning a Good classification and a Excellent health grade. Of those days, 324 (95%) fell in the Good band (AQI 0–50), 18 (5%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 29, while the worst single-day peak hit 95 (Moderate). Residents averaged about 28.4 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (342 days). Across the 2023–2025 trend window, the share of monitored days rated Good shifted by -1.4 points and the median AQI moved +0 points, placing the multi-year trajectory at stable. The worst single reading over the 2023–2025 window was AQI 95, moderate but never Unhealthy. Nearby counties show comparable readings: Cascade (59.8% good, AQI 46); Custer (87.2% good, AQI 40); Dawson (90.3% good, AQI 18); Fergus (90.7% good, AQI 41); Flathead (73.7% good, AQI 41); Gallatin (98.1% good, AQI 11).
Air Quality Summary
Good Days
94.7%
324 of 342 monitored days
19.7pp vs 75% target
Max AQI Recorded
95
Moderate
Health Grade
Excellent
90th-pct AQI 29
Beaverhead County, Good days share 94.7%
National avg
Share of monitored days at AQI 0-50 (Good band).
Beaverhead 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 342 monitored days across EPA AQI categories.
Good
324
95%
Moderate
18
5%
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 Beaverhead County.
- PM2.5 · 342 days · 100.0%
Health Impact Assessment
Excellent
Beaverhead County's air quality is rated Excellent based on 94.7% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 94.7% of monitored days in 2025, with a median AQI of 13. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM2.5, driving AQI on 342 of 342 monitored days.
5-Year Air Quality Trend
Air quality is stable in Beaverhead County. Highest Good-day share: 2023 (96.1%, 344 of 358 monitored days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2023 | 344 | 12 | 2 | 0 | 13 | 124 |
| 2024 | 298 | 46 | 0 | 2 | 12 | 180 |
| 2025 | 324 | 18 | 0 | 0 | 13 | 95 |
How does Beaverhead County compare?
How Beaverhead County compares
Good-day share better than US avg
Beaverhead County 94.7%
Navajo County, Arizona 99.5%
US average 76.0%
Median AQI better than US avg
Beaverhead County 13
Navajo County, Arizona 13
US average 39
Unhealthy days / yr better than US avg
Beaverhead County 0
Navajo County, Arizona 0
US average 1
Counties with a similar median AQI
Nationwide peers within about the same annual median AQI as Beaverhead County (13), not geographic neighbors.
Navajo County, Arizona
Median AQI 13 · 99.5% Good-day share
Park County, Wyoming
Median AQI 13 · 98.0% Good-day share
Hill County, Montana
Median AQI 14 · 92.1% Good-day share
Teton County, Montana
Median AQI 12 · 97.1% Good-day share
Gallatin County, Montana
Median AQI 11 · 98.1% Good-day share
Platte County, Wyoming
Median AQI 15 · 90.6% Good-day share
Same primary pollutant: PM2.5
PM2.5 led the AQI on the most monitored days here. These peers share that driver and the closest Good-day share (a second relationship type beyond median-AQI neighbors).
Potter County, Texas
94.1% Good-day share · median AQI 16
Kitsap County, Washington
95.5% Good-day share · median AQI 22
Whatcom County, Washington
94.0% Good-day share · median AQI 31
Routt County, Colorado
93.7% Good-day share · median AQI 22
Scotts Bluff County, Nebraska
95.8% Good-day share · median AQI 23
Thurston County, Washington
93.5% Good-day share · median AQI 27
Montana counties on the map
Geographic containment only, other monitored counties in Montana, independent of AQI or pollutant match.
What Beaverhead 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 13 means for exposure. Health guidance
- See how Beaverhead County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Beaverhead County with its Montana neighbours before drawing a conclusion about the region. All of Montana
Based on 342 EPA-monitored days in 2025; figures reflect only days the monitors reported. Source: EPA Air Quality System annual summaries.
Keep exploring the annual AQI record
Air-quality reading list
Frequently Asked Questions
What is the air quality in Beaverhead County, Montana? ▼
Beaverhead County has a median Air Quality Index (AQI) of 13, rated "Good." 94.7% of monitored days (324 out of 342) had good air quality in 2025.
What is the main pollutant in Beaverhead County? ▼
The primary pollutant in Beaverhead County is Fine Particles (PM2.5), which was the main AQI driver on 342 days (100% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Beaverhead County have? ▼
In 2025, Beaverhead County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 95.
Is the air quality in Beaverhead County getting better or worse? ▼
Air quality in Beaverhead County is stable across floor-qualifying years (2023-2025); years with fewer than 100 monitored days are excluded from that direction. Highest qualifying Good-day share: 2023 at 96.1% (344 of 358 days). Lowest qualifying Good-day share: 2024 at 86.1% (298 of 346 days).
What does AQI 13 mean for health? ▼
Beaverhead County's median AQI of 13 falls in the "Good" category. See the AQI category guide for what each range means for health.
How does Beaverhead County compare to other counties in Montana? ▼
Beaverhead County has 94.7% good air days. Nearby counties in Montana: Cascade (59.8% good), Custer (87.2% good), Dawson (90.3% good), Fergus (90.7% good), Flathead (73.7% good), Gallatin (98.1% good).
What is the 90th percentile AQI in Beaverhead County? ▼
The 90th percentile AQI for Beaverhead County is 29, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 95 (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. Spotted a figure that looks wrong? Report a correction.
Source: U.S. EPA Air Quality System (AQS) Annual AQI by county summary files for Beaverhead County, Montana · 2020–2025
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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.