| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 17°F | 34°F | 24°F | 1.9" |
| February | 17°F | 34°F | 25°F | 2.4" |
| March | 31°F | 52°F | 40°F | 3.0" |
| April | 41°F | 65°F | 52°F | 4.3" |
| May | 53°F | 75°F | 63°F | 6.0" |
| June | 62°F | 84°F | 72°F | 4.4" |
| July | 65°F | 86°F | 75°F | 7.8" |
| August | 63°F | 83°F | 72°F | 4.4" |
| September | 54°F | 78°F | 65°F | 5.3" |
| October | 44°F | 66°F | 53°F | 5.8" |
| November | 32°F | 52°F | 41°F | 3.9" |
| December | 21°F | 37°F | 28°F | 4.0" |
| Index | Sigourney | Iowa | National |
| Air quality index | 42 | 39 | 50 |
| Pollution index | 577,838 | 1,643,836 | 5,066,862 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 244 |
| Days with moderate air quality | 120 |
| Days w/ poor A.Q. for sensitive groups | 1 |
| Days with unhealthy air quality |
| Pollutant | Total |
| Arsenic | 0.000% |
| Benzene | 0.010% |
| Carbon Tetrachloride | 0.001% |
| Lead | 0.090% |
| Mercury | 0.000% |
| City, State | Population | Air Quality Index | National Avg. |
| Gibson, IA | 48 | 42 | 16% |
| Keota, IA | 932 | 42 | 16% |
| North English, IA | 1,148 | 42 | 16% |
| Rose Hill, IA | 160 | 42 | 16% |
| What Cheer, IA | 729 | 42 | 16% |
| Sigourney, IA | 2,105 | 42 | 16% |
| City, State | Population | Air Quality Index | National Avg. |
| Leetonia, OH | 2,105 | 45 | 10% |
| Boulevard Gardens, FL | 2,105 | 41 | 18% |
| Knightstown, IN | 2,105 | 365 | 630% |
| Jal, NM | 2,105 | 36 | 28% |
| Leechburg, PA | 2,105 | 36 | 28% |
| Sigourney, IA | 2,105 | 42 | 16% |