| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 19°F | 35°F | 27°F | 2.2" |
| February | 19°F | 37°F | 27°F | 2.0" |
| March | 30°F | 50°F | 39°F | 3.1" |
| April | 40°F | 64°F | 51°F | 3.5" |
| May | 51°F | 74°F | 62°F | 4.2" |
| June | 60°F | 82°F | 70°F | 5.2" |
| July | 62°F | 84°F | 73°F | 4.0" |
| August | 60°F | 83°F | 71°F | 3.4" |
| September | 53°F | 77°F | 64°F | 3.4" |
| October | 43°F | 65°F | 53°F | 3.4" |
| November | 32°F | 52°F | 42°F | 2.6" |
| December | 25°F | 41°F | 32°F | 3.0" |
| Index | Marion | Ohio | National |
| Air quality index | 41 | 40 | 42 |
| Pollution index | 2,158,180 | 4,472,386 | 2,726,193 |
| Measurement | Total |
| Days measured | 245 |
| Days with good air quality | 218 |
| Days with moderate air quality | 27 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.160% |
| Benzene | 0.030% |
| Carbon Tetrachloride | 0.003% |
| Lead | 0.010% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Marseilles, OH | 82 | 39 | 22.0% |
| Harpster, OH | 254 | 39 | 22.0% |
| New Bloomington, OH | 345 | 39 | 22.0% |
| La Rue, OH | 581 | 39 | 22.0% |
| Caledonia, OH | 665 | 41 | 18.0% |
| Marion, OH | 36,011 | 41 | 18.0% |
| City | Population | Air Quality Index | National Avg. |
| Franklin, WI | 36,013 | 44 | 12.0% |
| West Kelowna, BC | 36,030 | n/a | |
| San Juan Capistrano, CA | 35,976 | 89 | 78.0% |
| Lauderdale Lakes, FL | 36,063 | 41 | 18.0% |
| Panama City, FL | 35,952 | 38 | 24.0% |
| Marion, OH | 36,011 | 41 | 18.0% |
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