Median AQI
14
Good
Montana · County air quality · 2025
Dawson County, Montana
Median AQI 14 (Good). 95.0% of monitored days rated Good, direct from EPA Air Quality System stations.
- 14
- Median AQI
- 95.0%
- Good-air days
- 1
- Unhealthy days
- 89%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Dawson County's air is good on balance, cleaner than most US counties, a median AQI of 14 with 95.0% of 181 monitored days in the Good band, driven mainly by PM2.5.
- 14
- median AQI · Good
- 95.0%
- days rated Good
- PM2.5
- main pollutant
- 89%
- cleaner than US counties
1 day reached Unhealthy or worse; the worst single reading hit AQI 162.
Data updated July 2026
- Good · 172 d · 95.0%
- Moderate · 8 d · 4.4%
- Unhealthy · 1 d · 0.6%
How did Dawson County's air break down in 2025?
Across 181 monitored days, 172 fell in the Good band (AQI 0–50) and 1 reached Unhealthy or worse. The worst single day peaked at AQI 162 (Unhealthy).
EPA AQS →Air quality data from EPA Air Quality System (2025). 181 days monitored. Median AQI: 14 (Good).
Insights: Dawson County, Montana. EPA monitors recorded a median Air Quality Index of 14 across 181 measured days in 2025, earning a Good classification and a Excellent health grade. Of those days, 172 (95%) fell in the Good band (AQI 0–50), 8 (4%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 30, while the worst single-day peak hit 162 (Unhealthy). Residents averaged about 28.5 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (181 days). Across the 2024–2025 trend window, good days shifted by -149 and the median AQI moved +0 points, placing the multi-year trajectory at improving. Residents and visitors experienced 1 unhealthy-or-worse days combined, periods when the EPA recommends sensitive groups limit prolonged outdoor exertion. Nearby counties show comparable readings: Beaverhead (100.0% good, AQI 12); Custer (91.2% good, AQI 39); Fergus (92.2% good, AQI 44); Flathead (82.1% good, AQI 40); Gallatin (99.1% good, AQI 14); Glacier (96.4% good, AQI 22).
Air Quality Summary
Good Days
95.0%
172 of 181 monitored days
20.0pp vs 75% target
Max AQI Recorded
162
Unhealthy
Health Grade
Excellent
90th-pct AQI 30
Dawson County, Good days share 95.0%
National avg
Share of monitored days at AQI 0-50 (Good band).
Dawson County, Unhealthy-or-worse share 0.6%
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
172
95%
Moderate
8
4%
USG
0
0%
Unhealthy
1
1%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Dawson County.
- PM2.5 · 181 days · 100.0%
Health Impact Assessment
Excellent
Dawson County's air quality is rated Excellent based on 95.0% good air days. There were 1 unhealthy days in 2025 when outdoor activity should be limited.
Air quality is acceptable most days, but 0 days reached "Unhealthy for Sensitive Groups" (AQI 101-150) and peak AQI reached 162. Sensitive groups should monitor real-time conditions at AirNow.gov.
The dominant pollutant is PM2.5, driving AQI on 181 of 181 monitored days.
5-Year Air Quality Trend
Air quality is improving in Dawson County. Best year: 2024 (321 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2024 | 321 | 33 | 3 | 0 | 14 | 120 |
| 2025 | 172 | 8 | 0 | 1 | 14 | 162 |
How does Dawson County compare?
How Dawson County compares
Good-day share better than US avg
Dawson County 95.0%
Beaverhead County, Montana 100.0%
US average 76.5%
Median AQI better than US avg
Dawson County 14
Beaverhead County, Montana 12
US average 38
Unhealthy days / yr worse than US avg
Dawson County 1
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 Dawson County.
Apache County, Arizona
AQI 14 · 99.6% good
Gallatin County, Montana
AQI 14 · 99.1% good
Hughes County, South Dakota
AQI 14 · 94.4% good
Klickitat County, Washington
AQI 14 · 84.2% good
Park County, Wyoming
AQI 14 · 99.5% good
Platte County, Wyoming
AQI 14 · 87.7% good
What Dawson County's air means for you
On most days the air here is fine, but PM2.5 drives 1 unhealthy-or-worse day a year that sensitive groups should plan around.
- Sensitive groups (asthma, heart conditions, children, older adults) should check the AQI on high-PM2.5 days, the guide explains what a median of 14 means for exposure. Health guidance
- See how Dawson County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Dawson 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 Dawson County, Montana? ▼
Dawson County has a median Air Quality Index (AQI) of 14, rated "Good." 95.0% of monitored days (172 out of 181) had good air quality in 2025.
What is the main pollutant in Dawson County? ▼
The primary pollutant in Dawson County is Fine Particles (PM2.5), which was the main AQI driver on 181 days (100% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Dawson County have? ▼
In 2025, Dawson County recorded 1 unhealthy air days (1 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 162.
Is the air quality in Dawson County getting better or worse? ▼
Air quality in Dawson County is improving based on 5-year trends (2024-2025). Best year: 2024 with 321 good days. Worst year: 2025 with 172 good days.
What does AQI 14 mean for health? ▼
Dawson County's median AQI of 14 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 Dawson County compare to other counties in Montana? ▼
Dawson County has 95.0% good air days. Nearby counties in Montana: Beaverhead (100.0% good), Custer (91.2% good), Fergus (92.2% good), Flathead (82.1% good), Gallatin (99.1% good), Glacier (96.4% good).
What is the 90th percentile AQI in Dawson County? ▼
The 90th percentile AQI for Dawson County is 30, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 162 (Unhealthy).
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.