| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 31°F | 54°F | 41°F | 5.0" |
| February | 32°F | 57°F | 44°F | 3.9" |
| March | 41°F | 67°F | 53°F | 4.8" |
| April | 49°F | 77°F | 62°F | 6.0" |
| May | 57°F | 83°F | 69°F | 3.7" |
| June | 66°F | 91°F | 78°F | 3.4" |
| July | 70°F | 92°F | 80°F | 5.5" |
| August | 70°F | 92°F | 80°F | 4.2" |
| September | 63°F | 87°F | 73°F | 4.5" |
| October | 50°F | 76°F | 62°F | 4.3" |
| November | 38°F | 65°F | 51°F | 4.5" |
| December | 35°F | 56°F | 45°F | 6.5" |
| Index | Charleston | Tennessee | National |
| Air quality index | 1 | 76 | 42 |
| Pollution index | 271,356 | 2,454,916 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 363 |
| Days with moderate air quality | 2 |
| Days w/ poor A.Q. for sensitive groups | |
| Days with unhealthy air quality |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.004% |
| Carbon Tetrachloride | 0.001% |
| Lead | 0.000% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Dayton, TN | 7,357 | 1 | 98.0% |
| South Cleveland, TN | 7,792 | 1 | 98.0% |
| Calhoun, TN | 674 | 1 | 98.0% |
| Benton, TN | 1,256 | 1 | 98.0% |
| Wildwood Lake, TN | 3,614 | 1 | 98.0% |
| Charleston, TN | 668 | 1 | 98.0% |
| City | Population | Air Quality Index | National Avg. |
| Blandinsville, IL | 668 | 29 | 42.0% |
| Cedar Vale, KS | 668 | 40 | 20.0% |
| Howard, KS | 668 | 40 | 20.0% |
| Argyle, MN | 668 | 33 | 34.0% |
| Pleasant Hope, MO | 668 | 39 | 22.0% |
| Charleston, TN | 668 | 1 | 98.0% |
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