| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 22°F | 38°F | 30°F | 3.0" |
| February | 22°F | 40°F | 31°F | 2.8" |
| March | 33°F | 53°F | 42°F | 4.5" |
| April | 43°F | 66°F | 54°F | 4.5" |
| May | 52°F | 75°F | 63°F | 4.1" |
| June | 61°F | 83°F | 72°F | 4.9" |
| July | 63°F | 85°F | 73°F | 4.0" |
| August | 61°F | 84°F | 72°F | 3.3" |
| September | 55°F | 79°F | 66°F | 3.3" |
| October | 44°F | 67°F | 55°F | 4.1" |
| November | 33°F | 55°F | 43°F | 3.3" |
| December | 27°F | 43°F | 34°F | 3.9" |
| Index | Hillsboro | Ohio | National |
| Air quality index | 43 | 40 | 42 |
| Pollution index | 735,656 | 4,472,386 | 2,726,193 |
| Measurement | Total |
| Days measured | 244 |
| Days with good air quality | 203 |
| Days with moderate air quality | 41 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.030% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.003% |
| Mercury | 0.150% |
| City | Population | Air Quality Index | National Avg. |
| Sinking Spring, OH | 277 | 38 | 24.0% |
| Rocky Fork Point, OH | 670 | 38 | 24.0% |
| Leesburg, OH | 1,449 | 38 | 24.0% |
| Cynthiana, OH | 29 | 38 | 24.0% |
| Greenfield, OH | 4,184 | 38 | 24.0% |
| Hillsboro, OH | 6,535 | 43 | 14.0% |
| City | Population | Air Quality Index | National Avg. |
| Mount Vernon, IN | 6,535 | 45 | 10.0% |
| Northborough, MA | 6,532 | 40 | 20.0% |
| East Rochester, NY | 6,530 | 37 | 26.0% |
| Shannon, QC | 6,530 | n/a | |
| Camp Swift, TX | 6,529 | 44 | 12.0% |
| Hillsboro, OH | 6,535 | 43 | 14.0% |
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