Median AQI
15
Good
Montana · County air quality · 2025
Sanders County, Montana
Median AQI 15 (Good). 100.0% of monitored days rated Good, direct from EPA Air Quality System stations.
- 15
- 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, Sanders County's air is good on balance, among the cleanest 5% of US counties, a median AQI of 15 with 100.0% of 181 monitored days in the Good band, driven mainly by PM10.
- 15
- median AQI · Good
- 100.0%
- days rated Good
- PM10
- main pollutant
- 96%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 31.
Data updated July 2026
- Good · 181 d · 100.0%
How did Sanders County's air break down in 2025?
Across 181 monitored days, 181 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 31 (Good).
EPA AQS →Air quality data from EPA Air Quality System (2025). 181 days monitored. Median AQI: 15 (Good).
Insights: Sanders County, Montana. EPA monitors recorded a median Air Quality Index of 15 across 181 measured days in 2025, earning a Good classification and a Excellent health grade. Of those days, 181 (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 21, while the worst single-day peak hit 31 (Good). Residents averaged about 30.0 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM10 (181 days). Across the 2020–2025 trend window, good days shifted by -121 and the median AQI moved -16 points, placing the multi-year trajectory at improving. The worst single reading over the 2020–2025 window was AQI 31, 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%
181 of 181 monitored days
25.0pp vs 75% target
Max AQI Recorded
31
Good
Health Grade
Excellent
90th-pct AQI 21
Sanders County, Good days share 100.0%
National avg
Share of monitored days at AQI 0-50 (Good band).
Sanders 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 181 monitored days across EPA AQI categories.
Good
181
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 Sanders County.
- PM10 · 181 days · 100.0%
Health Impact Assessment
Excellent
Sanders 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 15. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM10, driving AQI on 181 of 181 monitored days.
5-Year Air Quality Trend
Air quality is improving in Sanders County. Best year: 2024 (339 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 302 | 56 | 1 | 4 | 31 | 261 |
| 2021 | 232 | 104 | 8 | 11 | 42 | 207 |
| 2022 | 266 | 94 | 2 | 3 | 36 | 188 |
| 2023 | 263 | 96 | 3 | 2 | 37 | 181 |
| 2024 | 339 | 25 | 0 | 0 | 21 | 69 |
| 2025 | 181 | 0 | 0 | 0 | 15 | 31 |
How does Sanders County compare?
How Sanders County compares
Good-day share better than US avg
Sanders County 100.0%
Beaverhead County, Montana 100.0%
US average 76.5%
Median AQI better than US avg
Sanders County 15
Beaverhead County, Montana 12
US average 38
Unhealthy days / yr about average
Sanders 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 Sanders County.
Pacific County, Washington
AQI 15 · 100.0% good
Apache County, Arizona
AQI 14 · 99.6% good
Chaves County, New Mexico
AQI 16 · 94.4% good
Dawson County, Montana
AQI 14 · 95.0% good
Gallatin County, Montana
AQI 14 · 99.1% good
Hughes County, South Dakota
AQI 14 · 94.4% good
What Sanders County's air means for you
The air here stays in the breathable range year-round, with PM10 the main thing to watch.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-PM10 days, the guide explains what a median of 15 means for exposure. Health guidance
- See how Sanders County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Sanders County with its Montana neighbours before drawing a conclusion about the region. All of Montana
Based on 181 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 Sanders County, Montana? ▼
Sanders County has a median Air Quality Index (AQI) of 15, rated "Good." 100.0% of monitored days (181 out of 181) had good air quality in 2025.
What is the main pollutant in Sanders County? ▼
The primary pollutant in Sanders County is Coarse Particles (PM10), which was the main AQI driver on 181 days (100% of monitored days). Irritates airways and can aggravate asthma and bronchitis.
How many unhealthy air days does Sanders County have? ▼
In 2025, Sanders County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 31.
Is the air quality in Sanders County getting better or worse? ▼
Air quality in Sanders County is improving based on 5-year trends (2020-2025). Best year: 2024 with 339 good days. Worst year: 2025 with 181 good days.
What does AQI 15 mean for health? ▼
Sanders County's median AQI of 15 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 Sanders County compare to other counties in Montana? ▼
Sanders 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 Sanders County? ▼
The 90th percentile AQI for Sanders County is 21, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 31 (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.