What Is the Air Quality in Missoula, Montana?
Missoula, Montana has an Air Quality Grade of C (fair) with a 5-year median AQI of 54. The dominant pollutant is Fine Particulate Matter (PM2.5), and air quality has been improving over the past decade.
Missoula, Montana Air Quality Snapshot
| Air Quality Grade | C54/100 |
| 5-Year Median AQI | 54 (Moderate) |
| Most Recent Median AQI (2023) | 53 (Moderate) |
| Dominant Pollutant | Fine Particulate Matter (PM2.5) |
| 10-Year Trend | Improving (-0.30 AQI/yr) |
| Unhealthy Days (last 5 yr) | 76 |
| National Rank (cleanest = #1) | #987 of 1,020 (97th most polluted percentile) |
| Montana Rank | #19 of 19 |
What Does the C Grade Mean?
Missoula, Montana earns a C — air quality is fair, but not great. With a 5-year median AQI of 54, the city sees a meaningful number of "Moderate" days each year, when the EPA flags air as a concern for unusually sensitive people.
Missoula, Montana's 5-year median AQI of 54 is 13 points above the national average of 41 — meaningfully more polluted than the typical U.S. metro tracked here. Within Montana, Missoula, Montana runs more polluted than the state average of 31 — local sources or geography are concentrating pollution above the state's typical reading.
For context within Montana: Rosebud, Montana currently holds the state's cleanest grade (A, AQI 23), while Sanders, Montana sits at the bottom (D, AQI 36).
What's in Missoula, Montana's Air?
The dominant pollutant in Missoula, Montana is Fine Particulate Matter (PM2.5). Fine particulate matter — particles less than 2.5 micrometers across — comes mostly from combustion: vehicle exhaust, wildfire smoke, residential wood burning, and industrial emissions. Because these particles are small enough to enter the bloodstream, PM2.5 is the pollutant most strongly linked to cardiovascular disease, respiratory illness, and premature death.
Days by Dominant Pollutant (2023)
| Pollutant | Days as Dominant | Share of Year |
|---|---|---|
| Fine Particulate Matter (PM2.5) | 297 | 82% |
| Ground-Level Ozone | 67 | 18% |
Is the Air Getting Better or Worse?
Air quality in Missoula, Montana has been improving over the past decade, with median AQI dropping by roughly 0.3 points per year. That is consistent with the broader national pattern — most U.S. metros have seen steady reductions in particulate and ozone pollution since the 2010s as cleaner vehicles and power plants come online.
In 2014, Missoula, Montana posted a median AQI of 52. By 2023 that figure was 53 — a rise of 1 AQI points dirtier across 10 years of EPA records.
Year-by-Year AQI in Missoula, Montana
| Year | Median AQI | Good Days | Unhealthy Days | Dominant Pollutant |
|---|---|---|---|---|
| 2014 | 52 | 173 | 18 | PM2.5 |
| 2015 | 56 | 126 | 23 | PM2.5 |
| 2016 | 58 | 72 | 25 | PM2.5 |
| 2017 | 65 | 52 | 73 | PM2.5 |
| 2018 | 54 | 146 | 4 | PM2.5 |
| 2019 | 52 | 173 | 4 | PM2.5 |
| 2020 | 54 | 155 | 19 | PM2.5 |
| 2021 | 56 | 122 | 30 | PM2.5 |
| 2022 | 54 | 149 | 15 | PM2.5 |
| 2023 | 53 | 156 | 8 | PM2.5 |
Health Context for Missoula, Montana
Across the past five years, this area has logged 76 days where AQI rose into the "Unhealthy for Sensitive Groups" range or worse — about 15 days per year. That is roughly typical for a U.S. metro, with most caution days clustered in summer (ozone) or wildfire season.
Healthy adults can continue normal outdoor activity in most weather, but should pay attention to AQI alerts during the worst pollution windows. People with asthma, heart disease, or pregnancy should reduce prolonged or intense outdoor exertion on flagged days, and consider running an indoor HEPA air cleaner during peak season. Because PM2.5 penetrates deep into the lungs and bloodstream, an N95 or KN95 mask provides meaningful protection on smoky or high-particulate days — surgical masks do not.
How This Grade Is Calculated
The AirHistory Air Quality Grade combines four signals: the 5-year median AQI (40% of the score), the 10-year trend direction (30%), the count of unhealthy days per year (20%), and the dominant pollutant type (10%). All four come directly from the EPA Air Quality System (AQS), which aggregates readings from federally certified monitors. Read the full methodology.
Missoula, Montana has an Air Quality Grade of C (fair) with a 5-year median AQI of 54. The dominant pollutant is Fine Particulate Matter (PM2.5), and air quality has been improving over the past decade.
The data source behind this answer is the EPA Air Quality System (AQS). Every figure on the page traces back to that source; the methodology page describes the inputs and the refresh cadence in full detail.
For readers turning this answer into action: cross-reference against the underlying the EPA Air Quality System (AQS) record before acting on time-sensitive decisions. The site renders the data as it was published; subsequent revisions can shift the picture, and the live federal data is always the authoritative current reference.
Source: EPA Outdoor Air Quality Data, 2026.