| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 16°F | 35°F | 24°F | 0.8" |
| February | 18°F | 37°F | 27°F | 1.3" |
| March | 32°F | 54°F | 41°F | 2.5" |
| April | 42°F | 65°F | 52°F | 4.9" |
| May | 52°F | 73°F | 62°F | 5.8" |
| June | 63°F | 83°F | 72°F | 6.1" |
| July | 66°F | 87°F | 76°F | 3.9" |
| August | 64°F | 84°F | 74°F | 6.4" |
| September | 56°F | 77°F | 66°F | 3.7" |
| October | 44°F | 65°F | 54°F | 3.3" |
| November | 33°F | 52°F | 41°F | 2.2" |
| December | 21°F | 38°F | 28°F | 2.0" |
| Index | Mercer | Missouri | National |
| Air quality index | 39 | 97 | 42 |
| Pollution index | 141,634 | 1,630,255 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 306 |
| Days with moderate air quality | 59 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.004% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.000% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Newtown, MO | 290 | 39 | 22.0% |
| Lucerne, MO | 42 | 39 | 22.0% |
| Davis City, IA | 255 | 39 | 22.0% |
| Allerton, IA | 453 | 39 | 22.0% |
| Powersville, MO | 60 | 39 | 22.0% |
| Mercer, MO | 323 | 39 | 22.0% |
| City | Population | Air Quality Index | National Avg. |
| Manalapan, FL | 323 | 36 | 28.0% |
| Barnum, IA | 323 | 37 | 26.0% |
| Medora, IL | 323 | 54 | 8.0% |
| Stinesville, IN | 323 | 42 | 16.0% |
| Montpelier, LA | 323 | 30 | 40.0% |
| Mercer, MO | 323 | 39 | 22.0% |
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