| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 8°F | 30°F | 17°F | 1.4" |
| February | 10°F | 33°F | 20°F | 0.9" |
| March | 20°F | 44°F | 31°F | 1.0" |
| April | 30°F | 57°F | 42°F | 1.0" |
| May | 39°F | 67°F | 52°F | 1.9" |
| June | 48°F | 75°F | 60°F | 2.6" |
| July | 54°F | 86°F | 69°F | 1.3" |
| August | 51°F | 83°F | 66°F | 1.4" |
| September | 43°F | 73°F | 56°F | 1.4" |
| October | 32°F | 59°F | 43°F | 0.8" |
| November | 19°F | 43°F | 29°F | 2.4" |
| December | 6°F | 26°F | 15°F | 1.5" |
| Index | Chester | Montana | National |
| Air quality index | 21 | 34 | 42 |
| Pollution index | 150,385 | 834,473 | 2,726,193 |
| Measurement | Total |
| Days measured | 363 |
| Days with good air quality | 350 |
| Days with moderate air quality | 12 |
| Days w/ poor A.Q. for sensitive groups | 1 |
| Days with unhealthy air quality | 0 |
| 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. |
| Inverness, MT | 34 | 21 | 58.0% |
| Joplin, MT | 242 | 21 | 58.0% |
| Chester, MT | 1,076 | 21 | 58.0% |
| City | Population | Air Quality Index | National Avg. |
| Douglas, AL | 1,076 | 43 | 14.0% |
| Woodville, AL | 1,076 | 44 | 12.0% |
| Wallace, ID | 1,076 | 43 | 14.0% |
| Arkport, NY | 1,076 | 35 | 30.0% |
| Baxter Estates, NY | 1,076 | 51 | 2.0% |
| Chester, MT | 1,076 | 21 | 58.0% |
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