Montana · County air quality · 2025

Glacier County, Montana

Median AQI 23 (Good). 91.7% of monitored days rated Good, direct from EPA Air Quality System stations.

23
Median AQI
91.7%
Good-air days
0
Unhealthy days
84%
Cleaner than US counties

Glacier County's 2025 annual median AQI is 23 (Good), with 91.7% Good days

According to the U.S. EPA Air Quality System, Glacier County, Montana posted a 2025 median AQI of 23 (Good) across 351 monitored days, with 91.7% 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
Glacier County's 91.7% Good-day share places it cleaner than 84% of US counties in 2025.
Closest median-AQI peer
Deschutes County (89.3% Good, median AQI 23) is the closest nationwide median-AQI peer to Glacier County.
2023–2025 trend
Glacier County's floor-qualifying Good-day share is worsening from 2023 to 2025 (89.0% → 91.7%).
Median AQI
Median AQI: 23

According to the 2025 EPA AQS county release on PlainAirData, Glacier County, Montana ranks #51 of 951 by median AQI (23) and #151 by good-day share (91.7%). Ponce County, Puerto Rico is #1 of 951 by median AQI (3, 91.4% Good days) at good-day-share #159 ≠ largest of 7 at 100.0% Good days #1 by good-day share (100.0%, median AQI 9) at median-AQI #7.

Annual release change

What changed in the 2025 EPA annual release

2024 → 2025
  • Glacier County's Good-day share rose from 88.4% to 91.7% between the 2024 and 2025 EPA annual releases, a change of +3.3 percentage points.
  • Glacier County's peak single-day AQI rose from 99 to 117 between the 2024 and 2025 EPA annual releases, a change of +18 points.

Compared against 346 monitored days in 2024 and 351 in 2025. These are arithmetic differences between two stored EPA annual summaries, not a cause claim or a live advisory.

National release changes Two-year CSV

Data updated August 2026

Glacier County AQI category distribution Stacked-segment bar showing the share of monitored days that fell in each EPA AQI category, Good, Moderate, USG, Unhealthy, Very Unhealthy, Hazardous, with median AQI marker. AQI category distribution 351 monitored days G Median AQI 23 0 50 100 150 200 300 500 Glacier County
  • Good · 322 d · 91.7%
  • Moderate · 26 d · 7.4%
  • USG · 3 d · 0.9%

How did Glacier County's air break down in 2025?

Across 351 monitored days, 322 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 →
Glacier County, Good days share 91.7%
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).

Where Glacier County sits nationally

COUNT-derived placement among 951 US counties with at least 100 monitored days in 2025. Glacier County's Good-day share is 91.7% - cleaner than 84% of that comparison set.

Glacier County Good-day share vs. every US county

Share of monitored days in the Good band (AQI 0–50) - EPA AQS annual release

91.7% Cleaner than 84% higher than 84% of 951 US counties

0.0%–5.0%: 0 US counties (0%). Below this entry. 5.0%–10.0%: 1 US counties (0%). Below this entry. 10.0%–15.0%: 4 US counties (0%). Below this entry. 15.0%–20.0%: 4 US counties (0%). Below this entry. 20.0%–25.0%: 1 US counties (0%). Below this entry. 25.0%–30.0%: 5 US counties (1%). Below this entry. 30.0%–35.0%: 9 US counties (1%). Below this entry. 35.0%–40.0%: 4 US counties (0%). Below this entry. 40.0%–45.0%: 16 US counties (2%). Below this entry. 45.0%–50.0%: 16 US counties (2%). Below this entry. 50.0%–55.0%: 32 US counties (3%). Below this entry. 55.0%–60.0%: 50 US counties (5%). Below this entry. 60.0%–65.0%: 77 US counties (8%). Below this entry. 65.0%–70.0%: 93 US counties (10%). Below this entry. 70.0%–75.0%: 109 US counties (11%). Below this entry. 75.0%–80.0%: 114 US counties (12%). Below this entry. 80.0%–85.0%: 123 US counties (13%). Below this entry. 85.0%–90.0%: 99 US counties (10%). Below this entry. 90.0%–95.0%: 117 US counties (12%). This entry sits in this band. 95.0%–100.0%: 70 US counties (7%). Above this entry. 100.0%–105.0%: 7 US counties (1%). Above this entry. This county 0.0% 100% every floor-qualified US county, bucketed by value

Each bar is a band; taller bars hold more US counties. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count, share, and where it sits relative to this entry.

Source U.S. Environmental Protection Agency, Air Quality System (AQS) · 2025

Pollutant Breakdown

Days where each pollutant was the primary driver of AQI readings in Glacier County.

Glacier County, Montana criteria pollutant distribution Stratified-band visualization showing the share of monitored days each criteria pollutant (PM2.5, PM10, O3, NO2, CO) was the primary AQI driver. PM2.5 · 100.0% 0% 25% 50% 75% 100% Glacier County, Montana · 351 monitored days Criteria pollutant column
  • PM2.5 · 351 days · 100.0%

2024 daily-monitor rhythm in Glacier County

Month-by-month median AQI from EPA day-level county monitors (346 reported days in 2024). Jul posted the highest typical readings (median AQI 46, peak 93); Jan was cleanest at median 12. Summer months (Jun–Aug) averaged median AQI 37 vs 18 in Dec–Feb.

0 10 20 30 40 50 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 12 21 25 31 19 21 46 43 26 23 24 21
Glacier County median daily AQI by calendar month (2024, EPA daily county file)

Health Impact Assessment

Excellent

Glacier County's air quality is rated Excellent based on 91.7% good air days. No unhealthy air days were recorded in 2025.

Air quality was acceptable on 91.7% of monitored days in 2025, with a median AQI of 23. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.

The dominant pollutant is PM2.5, driving AQI on 351 of 351 monitored days.

5-Year Air Quality Trend

Air quality is worsening in Glacier County. Highest Good-day share: 2025 (91.7%, 322 of 351 monitored days).

Year Good Moderate USG Unhealthy Median AQI
2023 315 33 5 1 12
2024 306 40 0 0 23
2025 322 26 3 0 23

How does Glacier County compare?

How Glacier County compares

Good-day share better than typical
Glacier County 91.7%
Deschutes County, Oregon 89.3%
Typical US county 76.0%
Median AQI better than typical
Glacier County 23
Deschutes County, Oregon 23
Typical US county 39
Unhealthy days / yr better than typical
Glacier County 0
Deschutes County, Oregon 1
Typical US county 1

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 Glacier 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.