Median AQI
16
Good
Montana · County air quality · 2025
Sanders County, Montana
Median AQI 16 (Good). 82.0% of monitored days rated Good, direct from EPA Air Quality System stations.
- 16
- Median AQI
- 82.0%
- Good-air days
- 0
- Unhealthy days
- 62%
- Cleaner than US counties
Sanders County's 2025 annual median AQI is 16 (Good), with 82.0% Good days
According to the U.S. EPA Air Quality System, Sanders County, Montana posted a 2025 median AQI of 16 (Good) across 345 monitored days, with 82.0% 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
- Sanders County's 82.0% Good-day share places it cleaner than 62% of US counties in 2025.
- Closest median-AQI peer
- Cook County (88.0% Good, median AQI 16) is the closest nationwide median-AQI peer to Sanders County.
- 2020–2025 trend
- Sanders County's floor-qualifying Good-day share is improving from 2020 to 2025 (83.2% → 82.0%).
- Median AQI
- Median AQI: 16
The verdict
According to EPA Air Quality System monitoring data, Sanders County's air is good on balance, cleaner than the median US county, a median AQI of 16 with 82.0% of 345 monitored days in the Good band, driven mainly by PM10.
- 16
- median AQI · Good
- 82.0%
- days rated Good
- PM10
- main pollutant
- 62%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 85.
Annual release change
What changed in the 2025 EPA annual release
- Sanders County's Good-day share fell from 93.1% to 82.0% between the 2024 and 2025 EPA annual releases, a change of -11.1 percentage points.
- Sanders County's median AQI fell from 21 to 16 between the 2024 and 2025 EPA annual releases, a change of -5 points.
- Sanders County's peak single-day AQI rose from 69 to 85 between the 2024 and 2025 EPA annual releases, a change of +16 points.
Data updated August 2026
- Good · 283 d · 82.0%
- Moderate · 62 d · 18.0%
How did Sanders County's air break down in 2025?
Across 345 monitored days, 283 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 85 (Moderate).
EPA AQS →Air quality data from EPA Air Quality System (2025). 345 days monitored. Median AQI: 16 (Good).
Insights: Sanders County, Montana. EPA monitors recorded a median Air Quality Index of 16 across 345 measured days in 2025, earning a Good classification and a Good health grade. Of those days, 283 (82%) fell in the Good band (AQI 0–50), 62 (18%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 55, while the worst single-day peak hit 85 (Moderate). Residents averaged about 24.6 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM10 (326 days), PM2.5 (19 days). Across the 2020–2025 trend window, the share of monitored days rated Good shifted by -0.5 points (measured against 366 monitored days in 2020 and 345 in 2025, so raw day counts are not comparable) and the median AQI moved -15 points, placing the multi-year trajectory at improving. The worst single reading over the 2020–2025 window was AQI 85, moderate but never Unhealthy. Nearby counties show comparable readings: Beaverhead (94.7% good, AQI 13); 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).
Air Quality Summary
Good Days
82.0%
283 of 345 monitored days
7.0pp vs 75% target
Max AQI Recorded
85
Moderate
Health Grade
Good
90th-pct AQI 55
Sanders County, Good days share 82.0%
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 345 monitored days across EPA AQI categories.
Good
283
82%
Moderate
62
18%
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 · 326 days · 94.5%
- PM2.5 · 19 days · 5.5%
Health Impact Assessment
Good
Sanders County's air quality is rated Good based on 82.0% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 82.0% of monitored days in 2025, with a median AQI of 16. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM10, driving AQI on 326 of 345 monitored days.
5-Year Air Quality Trend
Air quality is improving in Sanders County. Highest Good-day share: 2024 (93.1%, 339 of 364 monitored 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 | 283 | 62 | 0 | 0 | 16 | 85 |
How does Sanders County compare?
How Sanders County compares
Good-day share better than US avg
Sanders County 82.0%
Cook County, Minnesota 88.0%
US average 76.0%
Median AQI better than US avg
Sanders County 16
Cook County, Minnesota 16
US average 39
Unhealthy days / yr better than US avg
Sanders County 0
Cook County, Minnesota 8
US average 1
Counties with a similar median AQI
Nationwide peers within about the same annual median AQI as Sanders County (16), not geographic neighbors.
Cook County, Minnesota
Median AQI 16 · 88.0% Good-day share
Pacific County, Washington
Median AQI 16 · 99.7% Good-day share
Potter County, Texas
Median AQI 16 · 94.1% Good-day share
Taos County, New Mexico
Median AQI 16 · 98.9% Good-day share
Blaine County, Idaho
Median AQI 17 · 96.6% Good-day share
Luna County, New Mexico
Median AQI 17 · 84.7% Good-day share
Same primary pollutant: PM10
PM10 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).
Platte County, Wyoming
90.6% Good-day share · median AQI 15
Nye County, Nevada
92.6% Good-day share · median AQI 26
Mohave County, Arizona
94.8% Good-day share · median AQI 17
Putnam County, Florida
95.6% Good-day share · median AQI 21
Cass County, Nebraska
95.9% Good-day share · median AQI 19
Lincoln County, Wyoming
98.9% Good-day share · median AQI 10
Montana counties on the map
Geographic containment only, other monitored counties in Montana, independent of AQI or pollutant match.
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 16 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 345 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 Sanders County, Montana? ▼
Sanders County has a median Air Quality Index (AQI) of 16, rated "Good." 82.0% of monitored days (283 out of 345) 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 326 days (94% 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 85.
Is the air quality in Sanders County getting better or worse? ▼
Air quality in Sanders County is improving across floor-qualifying years (2020-2025); years with fewer than 100 monitored days are excluded from that direction. Highest qualifying Good-day share: 2024 at 93.1% (339 of 364 days). Lowest qualifying Good-day share: 2021 at 65.4% (232 of 356 days).
What does AQI 16 mean for health? ▼
Sanders County's median AQI of 16 falls in the "Good" category. See the AQI category guide for what each range means for health.
How does Sanders County compare to other counties in Montana? ▼
Sanders County has 82.0% good air days. Nearby counties in Montana: Beaverhead (94.7% good), Cascade (59.8% good), Custer (87.2% good), Dawson (90.3% good), Fergus (90.7% good), Flathead (73.7% good).
What is the 90th percentile AQI in Sanders County? ▼
The 90th percentile AQI for Sanders County is 55, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 85 (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 Sanders 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.