Median AQI
22
Good
Montana · County air quality · 2025
Glacier County, Montana
Median AQI 22 (Good). 96.4% of monitored days rated Good, direct from EPA Air Quality System stations.
- 22
- Median AQI
- 96.4%
- Good-air days
- 0
- Unhealthy days
- 92%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Glacier County's air is good on balance, among the cleanest 10% of US counties, a median AQI of 22 with 96.4% of 167 monitored days in the Good band, driven mainly by PM2.5.
- 22
- median AQI · Good
- 96.4%
- days rated Good
- PM2.5
- main pollutant
- 92%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 117.
Data updated July 2026
- Good · 161 d · 96.4%
- Moderate · 5 d · 3.0%
- USG · 1 d · 0.6%
How did Glacier County's air break down in 2025?
Across 167 monitored days, 161 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 117 (USG).
EPA AQS →Air quality data from EPA Air Quality System (2025). 167 days monitored. Median AQI: 22 (Good).
Insights: Glacier County, Montana. EPA monitors recorded a median Air Quality Index of 22 across 167 measured days in 2025, earning a Good classification and a Excellent health grade. Of those days, 161 (96%) fell in the Good band (AQI 0–50), 5 (3%) registered Moderate readings, and 1 (1%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 36, while the worst single-day peak hit 117 (USG). Residents averaged about 28.9 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (167 days). Across the 2023–2025 trend window, good days shifted by -154 and the median AQI moved +10 points, placing the multi-year trajectory at improving. The worst single reading over the 2023–2025 window was AQI 117, usg 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
96.4%
161 of 167 monitored days
21.4pp vs 75% target
Max AQI Recorded
117
USG
Health Grade
Excellent
90th-pct AQI 36
Glacier County, Good days share 96.4%
National avg
Share of monitored days at AQI 0-50 (Good band).
Glacier 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 167 monitored days across EPA AQI categories.
Good
161
96%
Moderate
5
3%
USG
1
1%
Unhealthy
0
0%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Glacier County.
- PM2.5 · 167 days · 100.0%
Health Impact Assessment
Excellent
Glacier County's air quality is rated Excellent based on 96.4% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 96.4% of monitored days in 2025, with a median AQI of 22. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM2.5, driving AQI on 167 of 167 monitored days.
5-Year Air Quality Trend
Air quality is improving in Glacier County. Best year: 2023 (315 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2023 | 315 | 33 | 5 | 1 | 12 | 166 |
| 2024 | 306 | 40 | 0 | 0 | 23 | 99 |
| 2025 | 161 | 5 | 1 | 0 | 22 | 117 |
How does Glacier County compare?
How Glacier County compares
Good-day share better than US avg
Glacier County 96.4%
Beaverhead County, Montana 100.0%
US average 76.5%
Median AQI better than US avg
Glacier County 22
Beaverhead County, Montana 12
US average 38
Unhealthy days / yr about average
Glacier 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 Glacier County.
Blaine County, Idaho
AQI 22 · 99.4% good
Cass County, Minnesota
AQI 22 · 94.4% good
Chase County, Kansas
AQI 22 · 88.9% good
Deschutes County, Oregon
AQI 22 · 93.4% good
Douglas County, Nevada
AQI 22 · 90.9% good
Franklin County, Idaho
AQI 22 · 95.8% good
What Glacier 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 22 means for exposure. Health guidance
- See how Glacier County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Glacier County with its Montana neighbours before drawing a conclusion about the region. All of Montana
Based on 167 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 Glacier County, Montana? ▼
Glacier County has a median Air Quality Index (AQI) of 22, rated "Good." 96.4% of monitored days (161 out of 167) had good air quality in 2025.
What is the main pollutant in Glacier County? ▼
The primary pollutant in Glacier County is Fine Particles (PM2.5), which was the main AQI driver on 167 days (100% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Glacier County have? ▼
In 2025, Glacier County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 117.
Is the air quality in Glacier County getting better or worse? ▼
Air quality in Glacier County is improving based on 5-year trends (2023-2025). Best year: 2023 with 315 good days. Worst year: 2025 with 161 good days.
What does AQI 22 mean for health? ▼
Glacier County's median AQI of 22 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 Glacier County compare to other counties in Montana? ▼
Glacier County has 96.4% 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 Glacier County? ▼
The 90th percentile AQI for Glacier County is 36, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 117 (USG).
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.