| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 22°F | 42°F | 31°F | 0.7" |
| February | 24°F | 45°F | 33°F | 1.3" |
| March | 38°F | 59°F | 47°F | 2.5" |
| April | 47°F | 68°F | 56°F | 4.5" |
| May | 56°F | 76°F | 65°F | 5.7" |
| June | 66°F | 86°F | 76°F | 5.1" |
| July | 70°F | 89°F | 79°F | 4.6" |
| August | 68°F | 88°F | 77°F | 4.7" |
| September | 60°F | 80°F | 69°F | 3.4" |
| October | 48°F | 69°F | 58°F | 3.5" |
| November | 38°F | 57°F | 46°F | 2.0" |
| December | 26°F | 44°F | 34°F | 1.5" |
| Index | Napoleon | Missouri | National |
| Air quality index | 47 | 97 | 42 |
| Pollution index | 609,001 | 1,630,255 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 210 |
| Days with moderate air quality | 154 |
| Days w/ poor A.Q. for sensitive groups | 1 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.001% |
| Benzene | 0.010% |
| Carbon Tetrachloride | 0.002% |
| Lead | 0.000% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Hardin, MO | 655 | 47 | 6.0% |
| Wood Heights, MO | 746 | 47 | 6.0% |
| Bates City, MO | 160 | 47 | 6.0% |
| Levasy, MO | 68 | 47 | 6.0% |
| Wellington, MO | 632 | 47 | 6.0% |
| Napoleon, MO | 162 | 47 | 6.0% |
| City | Population | Air Quality Index | National Avg. |
| Beatrice, AL | 162 | 52 | 4.0% |
| Chapin, IA | 162 | 15 | 70.0% |
| Colburn, IN | 162 | 42 | 16.0% |
| Tampa, KS | 162 | 22 | 56.0% |
| Nebo, KY | 162 | 43 | 14.0% |
| Napoleon, MO | 162 | 47 | 6.0% |
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