| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 15°F | 34°F | 25°F | 3.1" |
| February | 16°F | 36°F | 25°F | 3.1" |
| March | 29°F | 50°F | 38°F | 4.2" |
| April | 40°F | 65°F | 52°F | 7.0" |
| May | 50°F | 74°F | 62°F | 5.1" |
| June | 60°F | 81°F | 70°F | 5.3" |
| July | 61°F | 81°F | 71°F | 4.8" |
| August | 59°F | 81°F | 69°F | 8.6" |
| September | 52°F | 78°F | 64°F | 5.3" |
| October | 43°F | 67°F | 54°F | 7.0" |
| November | 31°F | 51°F | 40°F | 4.4" |
| December | 26°F | 42°F | 34°F | 4.5" |
| Index | Richwood | Ohio | National |
| Air quality index | 46 | 40 | 42 |
| Pollution index | 2,158,180 | 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 | 0.160% |
| Benzene | 0.030% |
| Carbon Tetrachloride | 0.003% |
| Lead | 0.010% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| La Rue, OH | 581 | 39 | 22.0% |
| Mount Victory, OH | 666 | 39 | 22.0% |
| New Bloomington, OH | 345 | 39 | 22.0% |
| Ridgeway, OH | 349 | 39 | 22.0% |
| Waldo, OH | 362 | 41 | 18.0% |
| Richwood, OH | 2,414 | 46 | 8.0% |
| City | Population | Air Quality Index | National Avg. |
| Herald Harbor, MD | 2,414 | 46 | 8.0% |
| Excelsior, MN | 2,414 | 46 | 8.0% |
| Wright-Patterson AFB, OH | 2,414 | 47 | 6.0% |
| Edgemont Park, MI | 2,413 | 36 | 28.0% |
| Bayard, NM | 2,415 | 37 | 26.0% |
| Richwood, OH | 2,414 | 46 | 8.0% |
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