Median AQI
45
Good
Montana · County air quality · 2025
Lincoln County, Montana
Median AQI 45 (Good). 54.5% of monitored days rated Good, direct from EPA Air Quality System stations.
- 45
- Median AQI
- 54.5%
- Good-air days
- 0
- Unhealthy days
- 10%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Lincoln County's air is good on balance, among the more polluted 10% of US counties, a median AQI of 45 with 54.5% of 176 monitored days in the Good band, driven mainly by PM2.5.
- 45
- median AQI · Good
- 54.5%
- days rated Good
- PM2.5
- main pollutant
- 10%
- cleaner than US counties
Not one day crossed into the Unhealthy tier; the worst single reading was AQI 92.
Data updated July 2026
- Good · 96 d · 54.5%
- Moderate · 80 d · 45.5%
How did Lincoln County's air break down in 2025?
Across 176 monitored days, 96 fell in the Good band (AQI 0–50) and 0 reached Unhealthy or worse. The worst single day peaked at AQI 92 (Moderate).
EPA AQS →Air quality data from EPA Air Quality System (2025). 176 days monitored. Median AQI: 45 (Good).
Insights: Lincoln County, Montana. EPA monitors recorded a median Air Quality Index of 45 across 176 measured days in 2025, earning a Good classification and a Moderate health grade. Of those days, 96 (55%) fell in the Good band (AQI 0–50), 80 (45%) registered Moderate readings, and 0 (0%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 67, while the worst single-day peak hit 92 (Moderate). Residents averaged about 16.4 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as PM2.5 (176 days). Across the 2020–2025 trend window, good days shifted by -79 and the median AQI moved -7 points, placing the multi-year trajectory at improving. The worst single reading over the 2020–2025 window was AQI 92, moderate 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
54.5%
96 of 176 monitored days
-20.5pp vs 75% target
Max AQI Recorded
92
Moderate
Health Grade
Moderate
90th-pct AQI 67
Lincoln County, Good days share 54.5%
National avg
Share of monitored days at AQI 0-50 (Good band).
Lincoln 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 176 monitored days across EPA AQI categories.
Good
96
55%
Moderate
80
45%
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 Lincoln County.
- PM2.5 · 176 days · 100.0%
Health Impact Assessment
Moderate
Lincoln County's air quality is rated Moderate based on 54.5% good air days. No unhealthy air days were recorded in 2025.
Air quality was acceptable on 54.5% of monitored days in 2025, with a median AQI of 45. Unusually sensitive people can check real-time conditions at AirNow.gov during high-pollution events.
The dominant pollutant is PM2.5, driving AQI on 176 of 176 monitored days.
5-Year Air Quality Trend
Air quality is improving in Lincoln County. Best year: 2024 (185 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 175 | 182 | 2 | 4 | 52 | 403 |
| 2021 | 125 | 223 | 11 | 6 | 56 | 177 |
| 2022 | 184 | 175 | 4 | 2 | 49 | 174 |
| 2023 | 151 | 209 | 2 | 2 | 53 | 189 |
| 2024 | 185 | 178 | 2 | 0 | 49 | 116 |
| 2025 | 96 | 80 | 0 | 0 | 45 | 92 |
How does Lincoln County compare?
How Lincoln County compares
Good-day share worse than US avg
Lincoln County 54.5%
Beaverhead County, Montana 100.0%
US average 76.5%
Median AQI worse than US avg
Lincoln County 45
Beaverhead County, Montana 12
US average 38
Unhealthy days / yr about average
Lincoln 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 Lincoln County.
Adair County, Oklahoma
AQI 45 · 59.2% good
Allen County, Indiana
AQI 45 · 58.2% good
Atascosa County, Texas
AQI 45 · 58.0% good
Baker County, Florida
AQI 45 · 69.1% good
Carson City County, Nevada
AQI 45 · 79.3% good
Clinton County, Iowa
AQI 45 · 59.9% good
What Lincoln 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 45 means for exposure. Health guidance
- See how Lincoln County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Lincoln County with its Montana neighbours before drawing a conclusion about the region. All of Montana
Based on 176 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 Lincoln County, Montana? ▼
Lincoln County has a median Air Quality Index (AQI) of 45, rated "Good." 54.5% of monitored days (96 out of 176) had good air quality in 2025.
What is the main pollutant in Lincoln County? ▼
The primary pollutant in Lincoln County is Fine Particles (PM2.5), which was the main AQI driver on 176 days (100% of monitored days). Penetrates deep into lungs and bloodstream. Linked to heart disease and premature death.
How many unhealthy air days does Lincoln County have? ▼
In 2025, Lincoln County recorded 0 unhealthy air days (0 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 92.
Is the air quality in Lincoln County getting better or worse? ▼
Air quality in Lincoln County is improving based on 5-year trends (2020-2025). Best year: 2024 with 185 good days. Worst year: 2025 with 96 good days.
What does AQI 45 mean for health? ▼
Lincoln County's median AQI of 45 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 Lincoln County compare to other counties in Montana? ▼
Lincoln County has 54.5% 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 Lincoln County? ▼
The 90th percentile AQI for Lincoln County is 67, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 92 (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.
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.