| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 19°F | 43°F | 30°F | 0.8" |
| February | 21°F | 46°F | 33°F | 1.6" |
| March | 34°F | 60°F | 46°F | 2.8" |
| April | 44°F | 69°F | 56°F | 4.4" |
| May | 53°F | 77°F | 65°F | 5.4" |
| June | 64°F | 87°F | 75°F | 5.6" |
| July | 68°F | 90°F | 79°F | 4.9" |
| August | 66°F | 89°F | 77°F | 5.7" |
| September | 57°F | 82°F | 69°F | 4.8" |
| October | 45°F | 71°F | 57°F | 3.9" |
| November | 34°F | 59°F | 46°F | 2.0" |
| December | 22°F | 44°F | 32°F | 1.8" |
| Index | Iatan | Missouri | National |
| Air quality index | 43 | 97 | 42 |
| Pollution index | 553,875 | 1,630,255 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 283 |
| Days with moderate air quality | 82 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.010% |
| Carbon Tetrachloride | 0.001% |
| Lead | 0.510% |
| Mercury | 0.000% |
| City | Population | Air Quality Index | National Avg. |
| De Kalb, MO | 440 | 43 | 14.0% |
| Atchison, KS | 10,561 | 43 | 14.0% |
| Easton, KS | 247 | 43 | 14.0% |
| Lewis and Clark Village, MO | 94 | 43 | 14.0% |
| Agency, MO | 704 | 43 | 14.0% |
| Iatan, MO | 16 | 43 | 14.0% |
| City | Population | Air Quality Index | National Avg. |
| Evansville, AK | 16 | 38 | 24.0% |
| Weston, CO | 16 | 15 | 70.0% |
| Ottosen, IA | 16 | 15 | 70.0% |
| Owasa, IA | 16 | 37 | 26.0% |
| Dover Hill, IN | 16 | 1 | 98.0% |
| Iatan, MO | 16 | 43 | 14.0% |
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