| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 15°F | 33°F | 24°F | 0.7" |
| February | 17°F | 36°F | 26°F | 1.1" |
| March | 31°F | 52°F | 40°F | 2.3" |
| April | 41°F | 65°F | 52°F | 4.7" |
| May | 51°F | 74°F | 62°F | 5.0" |
| June | 62°F | 83°F | 72°F | 6.5" |
| July | 65°F | 86°F | 75°F | 4.5" |
| August | 63°F | 84°F | 73°F | 5.2" |
| September | 54°F | 78°F | 65°F | 3.7" |
| October | 43°F | 65°F | 53°F | 3.0" |
| November | 32°F | 52°F | 41°F | 2.0" |
| December | 20°F | 36°F | 28°F | 1.9" |
| Index | Mystic | Iowa | National |
| Air quality index | 41 | 39 | 50 |
| Pollution index | 1,228,210 | 1,643,836 | 5,066,862 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 267 |
| Days with moderate air quality | 98 |
| Days w/ poor A.Q. for sensitive groups | |
| Days with unhealthy air quality |
| Pollutant | Total |
| Arsenic | 0.001% |
| Benzene | 0.010% |
| Carbon Tetrachloride | 0.001% |
| Lead | 0.001% |
| Mercury | 0.000% |
| City, State | Population | Air Quality Index | National Avg. |
| Moulton, IA | 653 | 40 | 20% |
| Cincinnati, IA | 314 | 41 | 18% |
| Rathbun, IA | 81 | 41 | 18% |
| Unionville, IA | 78 | 41 | 18% |
| Exline, IA | 154 | 41 | 18% |
| Mystic, IA | 363 | 41 | 18% |
| City, State | Population | Air Quality Index | National Avg. |
| Tumacacori-Carmen, AZ | 363 | 355 | 610% |
| Pleasanton, NE | 363 | 19 | 62% |
| Branch, AR | 363 | 35 | 30% |
| Hewlett Neck, NY | 363 | 53 | 6% |
| Lodi, NY | 363 | 32 | 36% |
| Mystic, IA | 363 | 41 | 18% |
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