| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 25°F | 41°F | 33°F | 7.5" |
| February | 18°F | 37°F | 27°F | 3.4" |
| March | 32°F | 53°F | 41°F | 6.9" |
| April | 39°F | 65°F | 51°F | 5.4" |
| May | 47°F | 76°F | 61°F | 3.1" |
| June | 59°F | 85°F | 72°F | 5.0" |
| July | 61°F | 85°F | 73°F | 5.3" |
| August | 63°F | 88°F | 74°F | 6.5" |
| September | 52°F | 83°F | 66°F | 4.5" |
| October | 46°F | 69°F | 56°F | 3.0" |
| November | 33°F | 55°F | 44°F | 6.9" |
| December | 24°F | 40°F | 32°F | 4.3" |
| Index | Chillicothe | Ohio | National |
| Air quality index | 38 | 40 | 42 |
| Pollution index | 2,306,000 | 4,472,386 | 2,726,193 |
| Measurement | Total |
| Days measured | 355 |
| Days with good air quality | 332 |
| Days with moderate air quality | 23 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| 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. |
| Richmond Dale, OH | 584 | 14 | 72.0% |
| Waverly, OH | 4,186 | 14 | 72.0% |
| Adelphi, OH | 371 | 25 | 50.0% |
| Laurelville, OH | 525 | 25 | 50.0% |
| Kingston, OH | 941 | 38 | 24.0% |
| Chillicothe, OH | 21,668 | 38 | 24.0% |
| City | Population | Air Quality Index | National Avg. |
| Alliance, OH | 21,671 | 46 | 8.0% |
| Raymore, MO | 21,676 | 47 | 6.0% |
| Gallup, NM | 21,637 | 17 | 66.0% |
| Roselle, NJ | 21,699 | 51 | 2.0% |
| Yucca Valley, CA | 21,701 | 89 | 78.0% |
| Chillicothe, OH | 21,668 | 38 | 24.0% |
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