Median AQI
39
Good
Montana · County air quality · 2025
Richland County, Montana
Median AQI 39 (Good). 86.7% of monitored days rated Good, direct from EPA Air Quality System stations.
- 39
- Median AQI
- 86.7%
- Good-air days
- 1
- Unhealthy days
- 69%
- Cleaner than US counties
The verdict
According to EPA Air Quality System monitoring data, Richland County's air is good on balance, cleaner than the median US county, a median AQI of 39 with 86.7% of 181 monitored days in the Good band, driven mainly by Ozone.
- 39
- median AQI · Good
- 86.7%
- days rated Good
- Ozone
- main pollutant
- 69%
- cleaner than US counties
1 day reached Unhealthy or worse; the worst single reading hit AQI 165.
Data updated July 2026
- Good · 157 d · 86.7%
- Moderate · 21 d · 11.6%
- USG · 2 d · 1.1%
- Unhealthy · 1 d · 0.6%
How did Richland County's air break down in 2025?
Across 181 monitored days, 157 fell in the Good band (AQI 0–50) and 1 reached Unhealthy or worse. The worst single day peaked at AQI 165 (Unhealthy).
EPA AQS →Air quality data from EPA Air Quality System (2025). 181 days monitored. Median AQI: 39 (Good).
Insights: Richland County, Montana. EPA monitors recorded a median Air Quality Index of 39 across 181 measured days in 2025, earning a Good classification and a Good health grade. Of those days, 157 (87%) fell in the Good band (AQI 0–50), 21 (12%) registered Moderate readings, and 2 (1%) reached Unhealthy for Sensitive Groups. The 90th-percentile AQI settled at 53, while the worst single-day peak hit 165 (Unhealthy). Residents averaged about 26.0 clean-air days per 30-day window during the monitoring year.
The full pollutant mix ranks as Ozone (139 days), PM2.5 (42 days). Across the 2020–2025 trend window, good days shifted by -186 and the median AQI moved +2 points, placing the multi-year trajectory at worsening. 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); 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
86.7%
157 of 181 monitored days
11.7pp vs 75% target
Max AQI Recorded
165
Unhealthy
Health Grade
Good
90th-pct AQI 53
Richland County, Good days share 86.7%
National avg
Share of monitored days at AQI 0-50 (Good band).
Richland 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
157
87%
Moderate
21
12%
USG
2
1%
Unhealthy
1
1%
Very Unhealthy
0
0%
Hazardous
0
0%
Pollutant Breakdown
Days where each pollutant was the primary driver of AQI readings in Richland County.
- Ozone · 139 days · 76.8%
- PM2.5 · 42 days · 23.2%
Health Impact Assessment
Good
Richland County's air quality is rated Good based on 86.7% good air days. There were 1 unhealthy days in 2025 when outdoor activity should be limited.
Air quality is acceptable most days, but 2 days reached "Unhealthy for Sensitive Groups" (AQI 101-150) and peak AQI reached 165. Sensitive groups should monitor real-time conditions at AirNow.gov.
The dominant pollutant is Ozone, driving AQI on 139 of 181 monitored days.
5-Year Air Quality Trend
Air quality is worsening in Richland County. Best year: 2020 (343 good days).
| Year | Good | Moderate | USG | Unhealthy | Median AQI | Max AQI |
|---|---|---|---|---|---|---|
| 2020 | 343 | 23 | 0 | 0 | 37 | 72 |
| 2021 | 284 | 63 | 4 | 0 | 38 | 147 |
| 2022 | 322 | 39 | 0 | 0 | 39 | 79 |
| 2023 | 267 | 87 | 5 | 4 | 39 | 219 |
| 2024 | 307 | 54 | 5 | 0 | 36 | 118 |
| 2025 | 157 | 21 | 2 | 1 | 39 | 165 |
How does Richland County compare?
How Richland County compares
Good-day share better than US avg
Richland County 86.7%
Beaverhead County, Montana 100.0%
US average 76.5%
Median AQI worse than US avg
Richland County 39
Beaverhead County, Montana 12
US average 38
Unhealthy days / yr worse than US avg
Richland 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 Richland County.
Ada County, Idaho
AQI 39 · 80.6% good
Aiken County, South Carolina
AQI 39 · 89.1% good
Albany County, New York
AQI 39 · 67.4% good
Alexander County, North Carolina
AQI 39 · 92.4% good
Ashland County, Wisconsin
AQI 39 · 85.6% good
Bennington County, Vermont
AQI 39 · 82.9% good
What Richland County's air means for you
On most days the air here is fine, but Ozone 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-Ozone days, the guide explains what a median of 39 means for exposure. Health guidance
- See how Richland County ranks against every monitored U.S. county on Good-day share. County rankings
- Compare Richland 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 Richland County, Montana? ▼
Richland County has a median Air Quality Index (AQI) of 39, rated "Good." 86.7% of monitored days (157 out of 181) had good air quality in 2025.
What is the main pollutant in Richland County? ▼
The primary pollutant in Richland County is Ozone (O3), which was the main AQI driver on 139 days (77% of monitored days). Can trigger asthma, reduce lung function, and cause chest pain.
How many unhealthy air days does Richland County have? ▼
In 2025, Richland County recorded 1 unhealthy air days (1 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 165.
Is the air quality in Richland County getting better or worse? ▼
Air quality in Richland County is worsening based on 5-year trends (2020-2025). Best year: 2020 with 343 good days. Worst year: 2025 with 157 good days.
What does AQI 39 mean for health? ▼
Richland County's median AQI of 39 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 Richland County compare to other counties in Montana? ▼
Richland County has 86.7% 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 Richland County? ▼
The 90th percentile AQI for Richland County is 53, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 165 (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.