| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 22°F | 36°F | 29°F | 2.2" |
| February | 22°F | 38°F | 29°F | 2.6" |
| March | 33°F | 51°F | 41°F | 4.9" |
| April | 43°F | 64°F | 53°F | 4.3" |
| May | 53°F | 74°F | 63°F | 5.0" |
| June | 61°F | 81°F | 71°F | 4.4" |
| July | 64°F | 82°F | 73°F | 8.1" |
| August | 62°F | 82°F | 72°F | 7.0" |
| September | 55°F | 76°F | 65°F | 5.2" |
| October | 44°F | 65°F | 54°F | 5.1" |
| November | 34°F | 53°F | 43°F | 4.0" |
| December | 27°F | 41°F | 34°F | 2.7" |
| Index | Harrisburg | Ohio | National |
| Air quality index | 46 | 40 | 42 |
| Pollution index | 2,306,000 | 4,472,386 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 237 |
| Days with moderate air quality | 127 |
| Days w/ poor A.Q. for sensitive groups | 1 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.710% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.003% |
| Lead | 0.020% |
| Mercury | 0.070% |
| City | Population | Air Quality Index | National Avg. |
| Darbyville, OH | 206 | 38 | 24.0% |
| Bloomingburg, OH | 966 | 38 | 24.0% |
| Mount Sterling, OH | 2,023 | 38 | 24.0% |
| Pancoastburg, OH | 43 | 38 | 24.0% |
| London, OH | 10,241 | 45 | 10.0% |
| Harrisburg, OH | 494 | 46 | 8.0% |
| City | Population | Air Quality Index | National Avg. |
| Sabula, IA | 494 | 42 | 16.0% |
| Centertown, KY | 494 | 43 | 14.0% |
| Fleming-Neon, KY | 494 | 45 | 10.0% |
| Supreme, LA | 494 | 41 | 18.0% |
| Guilford, ME | 494 | 31 | 38.0% |
| Harrisburg, OH | 494 | 46 | 8.0% |
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