| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 16°F | 38°F | 26°F | 0.1" |
| February | 19°F | 39°F | 28°F | 0.2" |
| March | 28°F | 52°F | 39°F | 0.3" |
| April | 33°F | 56°F | 43°F | 1.5" |
| May | 41°F | 65°F | 52°F | 2.3" |
| June | 51°F | 77°F | 63°F | 1.2" |
| July | 58°F | 86°F | 72°F | 0.8" |
| August | 55°F | 83°F | 69°F | 1.1" |
| September | 47°F | 74°F | 59°F | 1.1" |
| October | 37°F | 58°F | 46°F | 1.1" |
| November | 26°F | 47°F | 36°F | 0.2" |
| December | 14°F | 35°F | 24°F | 0.1" |
| Index | Belfry | Montana | National |
| Air quality index | 21 | 34 | 42 |
| Pollution index | 218,962 | 834,473 | 2,726,193 |
| Measurement | Total |
| Days measured | 362 |
| Days with good air quality | 357 |
| Days with moderate air quality | 4 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 1 |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.002% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.000% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Bridger, MT | 917 | 21 | 58.0% |
| Red Lodge, MT | 2,134 | 21 | 58.0% |
| Bridger CDP, MT | 20 | 21 | 58.0% |
| Roberts, MT | 298 | 21 | 58.0% |
| Bearcreek, MT | 144 | 21 | 58.0% |
| Belfry, MT | 304 | 21 | 58.0% |
| City | Population | Air Quality Index | National Avg. |
| Trapper Creek, AK | 304 | 31 | 38.0% |
| Mingo, IA | 304 | 39 | 22.0% |
| Onslow, IA | 304 | 39 | 22.0% |
| Fairview, KS | 304 | 43 | 14.0% |
| Oslo, MN | 304 | 33 | 34.0% |
| Belfry, MT | 304 | 21 | 58.0% |
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