| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 18°F | 34°F | 26°F | 2.9" |
| February | 20°F | 38°F | 28°F | 2.9" |
| March | 29°F | 50°F | 38°F | 3.4" |
| April | 39°F | 63°F | 50°F | 4.7" |
| May | 50°F | 74°F | 62°F | 4.8" |
| June | 58°F | 81°F | 69°F | 5.2" |
| July | 62°F | 84°F | 73°F | 3.8" |
| August | 60°F | 82°F | 71°F | 3.0" |
| September | 54°F | 77°F | 65°F | 3.3" |
| October | 44°F | 65°F | 54°F | 3.6" |
| November | 33°F | 53°F | 42°F | 3.4" |
| December | 25°F | 40°F | 32°F | 3.3" |
| Index | Flat Rock | Ohio | National |
| Air quality index | 40 | 40 | 42 |
| Pollution index | 2,402,580 | 4,472,386 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 291 |
| Days with moderate air quality | 73 |
| Days w/ poor A.Q. for sensitive groups | 1 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.001% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.005% |
| Lead | 0.020% |
| Mercury | 0.003% |
| City | Population | Air Quality Index | National Avg. |
| Monroeville, OH | 1,314 | 40 | 20.0% |
| Crystal Rock, OH | 164 | 40 | 20.0% |
| Castalia, OH | 1,142 | 40 | 20.0% |
| Stony Prairie, OH | 1,632 | 40 | 20.0% |
| Bellevue, OH | 7,928 | 40 | 20.0% |
| Flat Rock, OH | 261 | 40 | 20.0% |
| City | Population | Air Quality Index | National Avg. |
| Moro, AR | 261 | 45 | 10.0% |
| Acampo, CA | 261 | 45 | 10.0% |
| Lineville, IA | 261 | 39 | 22.0% |
| Shamrock Lakes, IN | 261 | 35 | 30.0% |
| Belfry, KY | 261 | 42 | 16.0% |
| Flat Rock, OH | 261 | 40 | 20.0% |
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