| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 32°F | 47°F | 38°F | 10.0" |
| February | 32°F | 49°F | 39°F | 6.9" |
| March | 41°F | 65°F | 51°F | 5.9" |
| April | 47°F | 69°F | 57°F | 4.6" |
| May | 58°F | 81°F | 69°F | 7.6" |
| June | 67°F | 88°F | 77°F | 5.8" |
| July | 69°F | 88°F | 77°F | 9.5" |
| August | 71°F | 92°F | 80°F | 9.0" |
| September | 62°F | 85°F | 72°F | 4.1" |
| October | 50°F | 73°F | 60°F | 11.0" |
| November | 39°F | 62°F | 49°F | 7.5" |
| December | 31°F | 47°F | 37°F | 8.3" |
| Index | Williamsville | Missouri | National |
| Air quality index | 26 | 97 | 42 |
| Pollution index | 3,633,480 | 1,630,255 | 2,726,193 |
| Measurement | Total |
| Days measured | 360 |
| Days with good air quality | 341 |
| Days with moderate air quality | 19 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.005% |
| Carbon Tetrachloride | 0.000% |
| Lead | 0.000% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Greenville, MO | 519 | 26 | 48.0% |
| Mill Spring, MO | 139 | 26 | 48.0% |
| Ellsinore, MO | 654 | 26 | 48.0% |
| Poplar Bluff, MO | 16,979 | 26 | 48.0% |
| Piedmont, MO | 3,550 | 54 | 8.0% |
| Williamsville, MO | 336 | 26 | 48.0% |
| City | Population | Air Quality Index | National Avg. |
| Delight, AR | 336 | 32 | 36.0% |
| Fargo, GA | 336 | 38 | 24.0% |
| Kempton, IN | 336 | 42 | 16.0% |
| Bradfordsville, KY | 336 | 40 | 20.0% |
| Bellflower, MO | 336 | 38 | 24.0% |
| Williamsville, MO | 336 | 26 | 48.0% |
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