| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 22°F | 37°F | 30°F | 7.1" |
| February | 17°F | 33°F | 25°F | 2.5" |
| March | 29°F | 49°F | 39°F | 4.5" |
| April | 38°F | 62°F | 50°F | 5.9" |
| May | 48°F | 74°F | 60°F | 3.3" |
| June | 60°F | 84°F | 72°F | 4.3" |
| July | 62°F | 85°F | 73°F | 5.0" |
| August | 63°F | 84°F | 73°F | 7.2" |
| September | 55°F | 79°F | 66°F | 6.6" |
| October | 47°F | 67°F | 56°F | 4.9" |
| November | 32°F | 52°F | 42°F | 5.1" |
| December | 22°F | 36°F | 29°F | 3.4" |
| Index | Marengo | Ohio | National |
| Air quality index | 41 | 40 | 42 |
| Pollution index | 2,158,180 | 4,472,386 | 2,726,193 |
| Measurement | Total |
| Days measured | 245 |
| Days with good air quality | 218 |
| Days with moderate air quality | 27 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| 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. |
| Fredericktown, OH | 2,510 | 41 | 18.0% |
| Waldo, OH | 362 | 41 | 18.0% |
| Hartford, OH | 355 | 41 | 18.0% |
| Ashley, OH | 1,672 | 41 | 18.0% |
| Fulton, OH | 255 | 41 | 18.0% |
| Marengo, OH | 269 | 41 | 18.0% |
| City | Population | Air Quality Index | National Avg. |
| Tuluksak, AK | 269 | 31 | 38.0% |
| Akron, AL | 269 | 35 | 30.0% |
| Axis, AL | 269 | 42 | 16.0% |
| Parkdale, AR | 269 | 34 | 32.0% |
| Midland, CO | 269 | 45 | 10.0% |
| Marengo, OH | 269 | 41 | 18.0% |
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