| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 25°F | 44°F | 33°F | 5.3" |
| February | 27°F | 47°F | 35°F | 4.6" |
| March | 37°F | 59°F | 47°F | 6.2" |
| April | 47°F | 69°F | 57°F | 9.5" |
| May | 55°F | 76°F | 65°F | 8.4" |
| June | 64°F | 86°F | 74°F | 6.1" |
| July | 67°F | 88°F | 77°F | 9.0" |
| August | 66°F | 87°F | 75°F | 9.8" |
| September | 58°F | 80°F | 68°F | 7.6" |
| October | 47°F | 69°F | 57°F | 7.0" |
| November | 37°F | 57°F | 46°F | 8.3" |
| December | 28°F | 45°F | 36°F | 4.6" |
| Index | Terre du Lac | Missouri | National |
| Air quality index | 54 | 97 | 42 |
| Pollution index | 753,473 | 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 | 0.001% |
| Lead | 0.020% |
| Mercury | 0.020% |
| City | Population | Air Quality Index | National Avg. |
| Bonne Terre, MO | 7,037 | 54 | 8.0% |
| Farmington, MO | 18,792 | 54 | 8.0% |
| Leadwood, MO | 1,579 | 54 | 8.0% |
| Iron Mountain Lake, MO | 705 | 54 | 8.0% |
| Caledonia, MO | 190 | 54 | 8.0% |
| Terre du Lac, MO | 2,382 | 54 | 8.0% |
| City | Population | Air Quality Index | National Avg. |
| Mitchellville, IA | 2,382 | 39 | 22.0% |
| Watertown, FL | 2,381 | 38 | 24.0% |
| Liberty, PA | 2,381 | 56 | 12.0% |
| Richwood, WV | 2,381 | 295 | 490.0% |
| Gray Summit, MO | 2,383 | 54 | 8.0% |
| Terre du Lac, MO | 2,382 | 54 | 8.0% |
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