| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 17°F | 39°F | 27°F | 0.5" |
| February | 19°F | 43°F | 29°F | 0.5" |
| March | 27°F | 54°F | 39°F | 1.1" |
| April | 34°F | 61°F | 46°F | 1.7" |
| May | 42°F | 70°F | 55°F | 3.0" |
| June | 51°F | 81°F | 65°F | 1.7" |
| July | 59°F | 92°F | 75°F | 0.9" |
| August | 56°F | 89°F | 72°F | 1.0" |
| September | 48°F | 79°F | 62°F | 1.6" |
| October | 38°F | 63°F | 49°F | 1.7" |
| November | 27°F | 50°F | 37°F | 0.8" |
| December | 16°F | 36°F | 25°F | 0.9" |
| Index | Roundup | Montana | National |
| Air quality index | 21 | 34 | 42 |
| Pollution index | 143,915 | 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 | 0.003% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.000% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Klein, MT | 156 | 21 | 58.0% |
| Camp Three, MT | 150 | 21 | 58.0% |
| Roundup, MT | 1,723 | 21 | 58.0% |
| City | Population | Air Quality Index | National Avg. |
| Duxbury, MA | 1,723 | 43 | 14.0% |
| Lakeland, MN | 1,723 | 46 | 8.0% |
| Bay Springs, MS | 1,723 | 36 | 28.0% |
| Lyman, WY | 1,723 | 44 | 12.0% |
| Hazen, AR | 1,724 | 45 | 10.0% |
| Roundup, MT | 1,723 | 21 | 58.0% |
Here are the best places to live in Montana
Check out the 10 safest cities in Montana
Check out the 10 most dangerous cities in Montana
Most Dangerous Cities In The US