| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 26°F | 43°F | 33°F | 9.7" |
| February | 27°F | 46°F | 35°F | 3.9" |
| March | 38°F | 62°F | 49°F | 4.6" |
| April | 45°F | 68°F | 56°F | 6.4" |
| May | 57°F | 79°F | 68°F | 3.6" |
| June | 66°F | 87°F | 76°F | 8.9" |
| July | 67°F | 90°F | 79°F | 2.3" |
| August | 70°F | 91°F | 80°F | 13.2" |
| September | 61°F | 83°F | 71°F | 7.3" |
| October | 49°F | 71°F | 59°F | 4.0" |
| November | 37°F | 59°F | 47°F | 4.3" |
| December | 26°F | 43°F | 34°F | 4.1" |
| Index | Hermann | Missouri | National |
| Air quality index | 39 | 97 | 42 |
| Pollution index | 732,008 | 1,630,255 | 2,726,193 |
| Measurement | Total |
| Days measured | 245 |
| Days with good air quality | 238 |
| Days with moderate air quality | 7 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.001% |
| Benzene | 0.020% |
| Carbon Tetrachloride | 0.001% |
| Lead | 0.000% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| Big Spring, MO | 227 | 39 | 22.0% |
| McKittrick, MO | 69 | 39 | 22.0% |
| Rhineland, MO | 107 | 39 | 22.0% |
| Jonesburg, MO | 812 | 39 | 22.0% |
| Danville, MO | 0 | 39 | 22.0% |
| Hermann, MO | 2,375 | 39 | 22.0% |
| City | Population | Air Quality Index | National Avg. |
| Piperton, TN | 2,375 | 45 | 10.0% |
| Whidbey Island Station, WA | 2,375 | 24 | 52.0% |
| Cimarron, KS | 2,376 | 15 | 70.0% |
| Stonewall, LA | 2,376 | 39 | 22.0% |
| Wray, CO | 2,377 | 45 | 10.0% |
| Hermann, MO | 2,375 | 39 | 22.0% |
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