Butte-Silver Bow, MT

EPA AQS → · NOAA →

Metro area air quality from EPA Air Quality System (2024). 366 days monitored. Median AQI: 31 (Good).

Insights: Butte-Silver Bow, MT metro. Aggregated EPA AQS monitors across this Core-Based Statistical Area logged a median Air Quality Index of 31 over 366 measured days in 2024, which corresponds to a Good band and a Moderate metro-wide health grade. The monitored-day split lands at 258 Good days (70%), 103 Moderate (28%), and 3 Unhealthy-for-Sensitive-Groups (1%). The 90th-percentile AQI finished at 66 while the highest single-day reading hit 168 (Unhealthy). Metro residents averaged roughly 21.1 clean-air days per 30-day window across the reporting year.

Across the 2020–2024 trend window, good days shifted by -31 and the median AQI moved +9 points, which classifies the multi-year trajectory as worsening. The metro recorded 2 unhealthy-or-worse days combined — on those days the EPA recommends that sensitive groups limit prolonged outdoor exertion, and many schools and athletic programs adjust outdoor activity accordingly. Metros with comparable AQI profiles include Dyersburg, TN (82.4% good, AQI 31); Lewiston-Auburn, ME (92.6% good, AQI 31); Pahrump, NV (87.2% good, AQI 31).

Air Quality Summary

Median AQI

31

Good

Good Days

70.5%

258 of 366 days

Max AQI

168

Unhealthy

Health Grade

Moderate

90th pct: 66

AQI Day Breakdown (2024)

Distribution of 366 monitored days across EPA AQI categories.

Good

258

70%

Moderate

103

28%

USG

3

1%

Unhealthy

2

1%

Very Unhealthy

0

0%

Hazardous

0

0%

Health Impact Assessment

Moderate

The Butte-Silver Bow, MT metro area's air quality is rated Moderate based on 70.5% good air days. There were 2 unhealthy days in 2024 when outdoor activity should be limited.

Air quality is acceptable most days, but 3 days reached "Unhealthy for Sensitive Groups" and peak AQI reached 168. Sensitive groups should monitor real-time conditions at AirNow.gov.

5-Year Air Quality Trend

Air quality is worsening in the Butte-Silver Bow, MT metro. Best year: 2020 (289 good days).

Year Good Moderate Unhealthy Median AQI
2020 289 69 3 22
2021 256 89 6 33
2022 268 87 2 27
2023 268 94 0 31
2024 258 103 2 31

Metros with Similar Air Quality

Metro areas across the US with a similar median AQI to Butte-Silver Bow, MT.

Dyersburg, TN

AQI 31 · 82.4% good

31

Lewiston-Auburn, ME

AQI 31 · 92.6% good

31

Pahrump, NV

AQI 31 · 87.2% good

31

Urban Honolulu, HI

AQI 31 · 98.4% good

31

Athens, TN

AQI 32 · 78.9% good

32

Clearlake, CA

AQI 32 · 99.5% good

32

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Air Quality Guides

Learn more about air quality monitoring, pollutants, and health impacts.

Understanding AQI

What each AQI level means and who is most at risk.

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Metro area air quality rankings and what drives urban pollution.

Health Effects of Air Pollution

How PM2.5 and ozone exposure affects respiratory and cardiovascular health.

Frequently Asked Questions

What is the air quality in the Butte-Silver Bow, MT metro area? ▼
The Butte-Silver Bow, MT metro area has a median Air Quality Index (AQI) of 31, rated "Good." 70.5% of monitored days (258 out of 366) had good air quality in 2024.
How many unhealthy air days does Butte-Silver Bow, MT have? ▼
In 2024, the Butte-Silver Bow, MT metro area recorded 2 unhealthy air days (2 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 168.
Is air quality in Butte-Silver Bow, MT getting better or worse? ▼
Air quality in the Butte-Silver Bow, MT metro is worsening based on 5-year trends (2020-2024). Best year: 2020 with 289 good days. Worst year: 2021 with 256 good days.
What does AQI 31 mean for health? ▼
An AQI of 31 is "Good" — air quality is satisfactory and poses little or no health risk. This is the best category on the EPA's AQI scale.
What is the 90th percentile AQI for Butte-Silver Bow, MT? ▼
The 90th percentile AQI for the Butte-Silver Bow, MT metro area is 66, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 168 (Unhealthy).
How does Butte-Silver Bow, MT compare to other metro areas? ▼
The Butte-Silver Bow, MT metro has 70.5% good air days. Similar metros: Dyersburg, TN (82.4% good), Lewiston-Auburn, ME (92.6% good), Pahrump, NV (87.2% good).

Data Sources

Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by CBSA dataset, 2020–2024. The AQS collects ambient air monitoring data from state, local, and tribal monitoring agencies across the United States.

Metrics: Air Quality Index (AQI) is calculated using EPA-standard breakpoints for six criteria pollutants: PM2.5, PM10, Ozone, NO2, CO, and SO2. Median AQI, max AQI, and 90th percentile AQI are computed from daily measurements. Good days percentage reflects days with AQI 0–50.

Coverage: 501 metro areas (Core Based Statistical Areas). Only metros with active monitoring stations are included. Unmonitored areas are not represented.

Read our methodology — how this data is sourced, computed, and verified.

Source: U.S. EPA — AirNow / AQS Air Quality Index readings and pollutant concentrations · 2025