Median AQI
9
Good
Montana · County air quality · 2025
Roosevelt County, Montana
Median AQI 9 (Good). 100.0% of monitored days rated Good, direct from EPA Air Quality System stations.
- 9
- Median AQI
- 100.0%
- Good-air days
- 0
- Unhealthy days
- 96%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Roosevelt County's air is good on balance, among the cleanest 5% of US counties, a median AQI of 9 with 100.0% of 17 monitored days in the Good band, driven mainly by PM2.5.
- 9
- median AQI · Good
- 100.0%
- days rated Good
- PM2.5
- main pollutant
- 96%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 38.
Data updated July 2026
- Good · 17 d · 100.0%
How did Roosevelt County's air break down in 2025?
Across 17 monitored days, 17 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 38 (Good).
EPA AQS →Air quality data from EPA Air Quality System (2025). 17 days monitored. Median AQI: 9 (Good).
Insights: Roosevelt County, Montana. EPA monitors recorded a median Air Quality Index of 9 across 17 measured days in 2025, earning a Good classification and a Excellent health grade. Of those days, 17 (100%) fell in the Good band (AQI 0–50), 0 (0%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 31, while the worst single-day peak hit 38 (Good). Residents averaged about 30.0 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (17 days). Across the 2020–2025 trend window, good days shifted by -57 and the median AQI moved -3 points, placing the multi-year trajectory at improving. The worst single reading over the 2020–2025 window was AQI 38, good but never Unhealthy. Nearby counties show comparable readings: Beaverhead (100.0% good, AQI 12); Custer (91.2% good, AQI 39); Dawson (95.0% good, AQI 14); Fergus (92.2% good, AQI 44); Flathead (82.1% good, AQI 40); Gallatin (99.1% good, AQI 14).
Air Quality Summary
Good Days
100.0%
17 of 17 monitored days
25.0pp vs 75% target
Max AQI Recorded
38
Good
Health Grade
Excellent
90th-pct AQI 31
Roosevelt County, Good days share 100.0%
National avg
Share of monitored days at AQI 0-50 (Good band).
Roosevelt 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 17 monitored days across EPA AQI categories.
Good
17
100%
Moderate
0
0%
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 Roosevelt County.
- PM2.5 · 17 days · 100.0%
Health Impact Assessment
Excellent
Roosevelt County's air quality is rated Excellent based on 100.0% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 100.0% of monitored days in 2025, with a median AQI of 9. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM2.5, driving AQI on 17 of 17 monitored days.
5-Year Air Quality Trend
Air quality is improving in Roosevelt County. Best year: 2022 (98 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 74 | 3 | 0 | 0 | 12 | 60 |
| 2021 | 89 | 11 | 0 | 0 | 16 | 99 |
| 2022 | 98 | 3 | 0 | 0 | 14 | 64 |
| 2023 | 62 | 9 | 0 | 1 | 13 | 161 |
| 2024 | 87 | 10 | 1 | 0 | 13 | 109 |
| 2025 | 17 | 0 | 0 | 0 | 9 | 38 |
How does Roosevelt County compare?
How Roosevelt County compares
Good-day share better than US avg
Roosevelt County 100.0%
Beaverhead County, Montana 100.0%
US average 76.5%
Median AQI better than US avg
Roosevelt County 9
Beaverhead County, Montana 12
US average 38
Unhealthy days / yr about average
Roosevelt County 0
Beaverhead County, Montana 0
US average 0
Other Counties in Montana
Air quality comparison for nearby counties in Montana.
Counties with Similar Air Quality
Counties across the US with a similar median AQI to Roosevelt County.
Carroll County, Virginia
AQI 9 · 100.0% good
Dakota County, Minnesota
AQI 9 · 93.4% good
Sonoma County, California
AQI 9 · 100.0% good
Thomas County, Nebraska
AQI 9 · 94.7% good
Catron County, New Mexico
AQI 8 · 100.0% good
Kenai Peninsula County, Alaska
AQI 8 · 100.0% good
What Roosevelt 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 9 means for exposure. Health guidance
- See how Roosevelt County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Roosevelt County with its Montana neighbours before drawing a conclusion about the region. All of Montana
Based on 17 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 Roosevelt County, Montana? ▼
Roosevelt County has a median Air Quality Index (AQI) of 9, rated "Good." 100.0% of monitored days (17 out of 17) had good air quality in 2025.
What is the main pollutant in Roosevelt County? ▼
The primary pollutant in Roosevelt County is Fine Particles (PM2.5), which was the main AQI driver on 17 days (100% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Roosevelt County have? ▼
In 2025, Roosevelt County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 38.
Is the air quality in Roosevelt County getting better or worse? ▼
Air quality in Roosevelt County is improving based on 5-year trends (2020-2025). Best year: 2022 with 98 good days. Worst year: 2025 with 17 good days.
What does AQI 9 mean for health? ▼
Roosevelt County's median AQI of 9 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 Roosevelt County compare to other counties in Montana? ▼
Roosevelt County has 100.0% good air days. Nearby counties in Montana: Beaverhead (100.0% good), Custer (91.2% good), Dawson (95.0% good), Fergus (92.2% good), Flathead (82.1% good), Gallatin (99.1% good).
What is the 90th percentile AQI in Roosevelt County? ▼
The 90th percentile AQI for Roosevelt County is 31, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 38 (Good).
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.