| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 13°F | 31°F | 21°F | 2.9" |
| February | 15°F | 33°F | 23°F | 2.6" |
| March | 29°F | 49°F | 38°F | 4.2" |
| April | 39°F | 62°F | 50°F | 6.5" |
| May | 51°F | 74°F | 61°F | 6.2" |
| June | 61°F | 82°F | 71°F | 7.9" |
| July | 64°F | 84°F | 73°F | 6.6" |
| August | 61°F | 82°F | 71°F | 9.8" |
| September | 53°F | 76°F | 64°F | 6.2" |
| October | 42°F | 64°F | 52°F | 6.1" |
| November | 30°F | 50°F | 39°F | 4.3" |
| December | 19°F | 34°F | 26°F | 4.0" |
| Index | Charlotte | Iowa | National |
| Air quality index | 53 | 39 | 50 |
| Pollution index | 1,592,910 | 1,643,836 | 5,066,862 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 158 |
| Days with moderate air quality | 204 |
| Days w/ poor A.Q. for sensitive groups | 3 |
| Days with unhealthy air quality |
| Pollutant | Total |
| Arsenic | 0.090% |
| Benzene | 0.030% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.010% |
| Mercury | 0.010% |
| City, State | Population | Air Quality Index | National Avg. |
| Clinton, IA | 26,148 | 53 | 6% |
| Preston, IA | 1,037 | 53 | 6% |
| Welton, IA | 151 | 53 | 6% |
| Andover, IA | 113 | 53 | 6% |
| Delmar, IA | 497 | 53 | 6% |
| Charlotte, IA | 404 | 53 | 6% |
| City, State | Population | Air Quality Index | National Avg. |
| New Germany, MN | 404 | 44 | 12% |
| Rocky Mountain, OK | 404 | 36 | 28% |
| Island, KY | 404 | 40 | 20% |
| Napakiak, AK | 404 | 29 | 42% |
| Weir, TX | 404 | 41 | 18% |
| Charlotte, IA | 404 | 53 | 6% |