| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 22°F | 44°F | 32°F | 1.3" |
| February | 26°F | 47°F | 35°F | 1.5" |
| March | 36°F | 60°F | 46°F | 3.3" |
| April | 46°F | 70°F | 57°F | 5.4" |
| May | 54°F | 76°F | 64°F | 5.8" |
| June | 64°F | 85°F | 74°F | 4.2" |
| July | 67°F | 89°F | 77°F | 4.9" |
| August | 65°F | 87°F | 75°F | 5.0" |
| September | 58°F | 80°F | 68°F | 3.1" |
| October | 47°F | 70°F | 57°F | 2.6" |
| November | 36°F | 57°F | 46°F | 3.3" |
| December | 28°F | 46°F | 36°F | 2.9" |
| Index | Sullivan | Missouri | National |
| Air quality index | 54 | 97 | 42 |
| Pollution index | 399,557 | 1,630,255 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 134 |
| Days with moderate air quality | 221 |
| Days w/ poor A.Q. for sensitive groups | 8 |
| Days with unhealthy air quality | 2 |
| Pollutant | Total |
| Arsenic | 0.001% |
| Benzene | 0.010% |
| Carbon Tetrachloride | 0.002% |
| Lead | 0.001% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Bourbon, MO | 1,866 | 39 | 22.0% |
| Leasburg, MO | 360 | 39 | 22.0% |
| St. Cloud, MO | 36 | 39 | 22.0% |
| Gerald, MO | 1,104 | 39 | 22.0% |
| West Sullivan, MO | 280 | 39 | 22.0% |
| Sullivan, MO | 6,499 | 54 | 8.0% |
| City | Population | Air Quality Index | National Avg. |
| De Queen, AR | 6,499 | 39 | 22.0% |
| San Martin, CA | 6,498 | 43 | 14.0% |
| Columbiana, OH | 6,498 | 42 | 16.0% |
| Bridgeport, TX | 6,498 | 33 | 34.0% |
| Nitro, WV | 6,498 | 40 | 20.0% |
| Sullivan, MO | 6,499 | 54 | 8.0% |
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