| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 11°F | 33°F | 20°F | 0.2" |
| February | 14°F | 37°F | 24°F | 0.2" |
| March | 25°F | 52°F | 36°F | 0.6" |
| April | 34°F | 62°F | 46°F | 1.6" |
| May | 43°F | 70°F | 56°F | 3.5" |
| June | 53°F | 82°F | 67°F | 2.6" |
| July | 61°F | 93°F | 76°F | 1.1" |
| August | 58°F | 90°F | 73°F | 1.1" |
| September | 48°F | 79°F | 62°F | 1.0" |
| October | 36°F | 62°F | 47°F | 1.0" |
| November | 23°F | 48°F | 34°F | 0.3" |
| December | 11°F | 32°F | 20°F | 0.2" |
| Index | Forsyth | Montana | National |
| Air quality index | 21 | 34 | 42 |
| Pollution index | 562,118 | 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 | 0.010% |
| Carbon Tetrachloride | 0.001% |
| Lead | 0.002% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Rosebud, MT | 36 | 39 | 22.0% |
| Forsyth, MT | 1,596 | 21 | 58.0% |
| City | Population | Air Quality Index | National Avg. |
| Wyoming, DE | 1,596 | 42 | 16.0% |
| Sarcoxie, MO | 1,596 | 37 | 26.0% |
| Penn State Erie (Behrend), PA | 1,596 | 36 | 28.0% |
| Minitonas-Bowsman, MB | 1,596 | n/a | |
| Georgiana, AL | 1,597 | 52 | 4.0% |
| Forsyth, MT | 1,596 | 21 | 58.0% |
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