What Is the Air Quality in Gallatin, Montana?
Gallatin, Montana has an Air Quality Grade of B (good) with a 5-year median AQI of 32. The dominant pollutant is Fine Particulate Matter (PM2.5), and air quality has been stable over the past decade.
Gallatin, Montana Air Quality Snapshot
| Air Quality Grade | B66/100 |
| 5-Year Median AQI | 32 (Good) |
| Most Recent Median AQI (2023) | 26 (Good) |
| Dominant Pollutant | Fine Particulate Matter (PM2.5) |
| 10-Year Trend | Stable (-0.04 AQI/yr) |
| Unhealthy Days (last 5 yr) | 30 |
| National Rank (cleanest = #1) | #154 of 1,020 (15th cleanest percentile) |
| Montana Rank | #9 of 19 |
What Does the B Grade Mean?
Gallatin, Montana earns a B — air quality is reliably in the safe range for most residents most of the time, with a 5-year median AQI of 32. Sensitive groups will see occasional caution days, but the typical resident will not need to change behavior based on air quality.
Gallatin, Montana's 5-year median AQI of 32 is 9 points below the national average of 41 — meaningfully cleaner than the typical U.S. metro tracked here. Within Montana, Gallatin, Montana's air quality is roughly typical for the state, where the average city posts a 5-year median AQI of 31.
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 Gallatin, Montana's Air?
The dominant pollutant in Gallatin, 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) | 362 | 99% |
| Nitrogen Dioxide | 3 | 1% |
Is the Air Getting Better or Worse?
Air quality in Gallatin, Montana has held roughly steady over the past decade, with year-to-year shifts in median AQI of less than half a point. That stability makes the city's long-run grade a reliable signal of what residents can expect day-to-day.
In 2014, Gallatin, Montana posted a median AQI of 33. By 2023 that figure was 26 — a drop of 7 AQI points cleaner across 10 years of EPA records.
Year-by-Year AQI in Gallatin, Montana
| Year | Median AQI | Good Days | Unhealthy Days | Dominant Pollutant |
|---|---|---|---|---|
| 2014 | 33 | 287 | 0 | PM2.5 |
| 2015 | 29 | 284 | 4 | PM2.5 |
| 2016 | 33 | 296 | 11 | PM2.5 |
| 2017 | 31 | 263 | 3 | PM2.5 |
| 2018 | 32 | 289 | 6 | PM2.5 |
| 2019 | 33 | 301 | 0 | PM2.5 |
| 2020 | 29 | 290 | 11 | PM2.5 |
| 2021 | 41 | 243 | 15 | PM2.5 |
| 2022 | 32 | 290 | 4 | PM2.5 |
| 2023 | 26 | 331 | 0 | PM2.5 |
Health Context for Gallatin, Montana
Across the past five years, this area has logged 30 days where AQI rose into the "Unhealthy for Sensitive Groups" range or worse — about 6 days per year. That is roughly typical for a U.S. metro, with most caution days clustered in summer (ozone) or wildfire season.
For most healthy adults, current air quality in this area does not require any change in behavior. People with severe asthma, COPD, or recent cardiac events should still keep an eye on daily AQI alerts, especially during wildfire 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.
Gallatin, Montana has an Air Quality Grade of B (good) with a 5-year median AQI of 32. The dominant pollutant is Fine Particulate Matter (PM2.5), and air quality has been stable 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.