| 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 | Washington Court House | Ohio | National |
| Air quality index | 38 | 40 | 42 |
| Pollution index | 735,656 | 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 | 0.010% |
| Benzene | 0.030% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.003% |
| Mercury | 0.150% |
| City | Population | Air Quality Index | National Avg. |
| Milledgeville, OH | 116 | 38 | 24.0% |
| New Holland, OH | 829 | 38 | 24.0% |
| Mount Sterling, OH | 2,023 | 38 | 24.0% |
| South Salem, OH | 221 | 38 | 24.0% |
| Octa, OH | 51 | 38 | 24.0% |
| Washington Court House, OH | 14,155 | 38 | 24.0% |
| City | Population | Air Quality Index | National Avg. |
| Weigelstown, PA | 14,156 | 41 | 18.0% |
| Anna, TX | 14,159 | 51 | 2.0% |
| Greendale, WI | 14,160 | 44 | 12.0% |
| Williamstown, NJ | 14,161 | 40 | 20.0% |
| Broadlands, VA | 14,146 | 47 | 6.0% |
| Washington Court House, OH | 14,155 | 38 | 24.0% |
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