| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 4°F | 28°F | 16°F | 0.5" |
| February | 8°F | 31°F | 18°F | 0.4" |
| March | 20°F | 47°F | 32°F | 0.6" |
| April | 30°F | 61°F | 44°F | 1.1" |
| May | 40°F | 70°F | 55°F | 2.9" |
| June | 50°F | 79°F | 64°F | 2.8" |
| July | 56°F | 90°F | 73°F | 1.8" |
| August | 54°F | 88°F | 70°F | 1.4" |
| September | 45°F | 77°F | 60°F | 1.2" |
| October | 32°F | 61°F | 45°F | 1.1" |
| November | 19°F | 45°F | 30°F | 0.6" |
| December | 5°F | 27°F | 15°F | 0.7" |
| Index | Glasgow | Montana | National |
| Air quality index | 34 | 34 | 42 |
| Pollution index | 348,172 | 834,473 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 309 |
| Days with moderate air quality | 53 |
| Days w/ poor A.Q. for sensitive groups | 3 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.005% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.010% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| St. Marie, MT | 325 | 34 | 32.0% |
| Fort Peck, MT | 246 | 34 | 32.0% |
| Nashua, MT | 326 | 34 | 32.0% |
| Glasgow, MT | 3,332 | 34 | 32.0% |
| City | Population | Air Quality Index | National Avg. |
| Lake Holm, WA | 3,332 | 45 | 10.0% |
| Nicholls, GA | 3,333 | 26 | 48.0% |
| Wyncote, PA | 3,333 | 51 | 2.0% |
| Winnsboro, TX | 3,330 | 37 | 26.0% |
| Port Ewen, NY | 3,334 | 36 | 28.0% |
| Glasgow, MT | 3,332 | 34 | 32.0% |
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