| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 22°F | 39°F | 30°F | 2.9" |
| February | 22°F | 40°F | 31°F | 2.3" |
| March | 34°F | 55°F | 44°F | 3.8" |
| April | 44°F | 68°F | 55°F | 5.1" |
| May | 54°F | 77°F | 65°F | 4.6" |
| June | 63°F | 85°F | 73°F | 6.3" |
| July | 64°F | 86°F | 75°F | 4.4" |
| August | 62°F | 85°F | 73°F | 3.0" |
| September | 56°F | 80°F | 67°F | 3.6" |
| October | 45°F | 68°F | 56°F | 3.5" |
| November | 34°F | 55°F | 44°F | 3.5" |
| December | 27°F | 43°F | 34°F | 4.1" |
| Index | Franklin | Indiana | National |
| Air quality index | 54 | 56 | 42 |
| Pollution index | 1,738,970 | 2,719,453 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 148 |
| Days with moderate air quality | 212 |
| Days w/ poor A.Q. for sensitive groups | 5 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.003% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.004% |
| Lead | 0.050% |
| Mercury | 0.010% |
| City | Population | Air Quality Index | National Avg. |
| Clifford, IN | 270 | 41 | 18.0% |
| Taylorsville, IN | 512 | 41 | 18.0% |
| Cordry Sweetwater Lakes, IN | 1,323 | 41 | 18.0% |
| Edinburgh, IN | 4,661 | 41 | 18.0% |
| Trafalgar, IN | 1,244 | 41 | 18.0% |
| Franklin, IN | 25,276 | 54 | 8.0% |
| City | Population | Air Quality Index | National Avg. |
| Suitland, MD | 25,273 | 47 | 6.0% |
| El Cerrito, CA | 25,280 | 40 | 20.0% |
| Prince Edward County, ON | 25,289 | n/a | |
| Clinton, IA | 25,290 | 42 | 16.0% |
| Mount Pleasant, MI | 25,290 | 26 | 48.0% |
| Franklin, IN | 25,276 | 54 | 8.0% |
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