| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 16°F | 33°F | 24°F | 0.5" |
| February | 18°F | 36°F | 26°F | 1.3" |
| March | 31°F | 52°F | 40°F | 7.8" |
| April | 41°F | 65°F | 52°F | 9.4" |
| May | 52°F | 74°F | 62°F | 8.4" |
| June | 62°F | 84°F | 72°F | 5.7" |
| July | 65°F | 87°F | 76°F | 6.6" |
| August | 63°F | 84°F | 73°F | 4.1" |
| September | 55°F | 79°F | 66°F | 7.3" |
| October | 43°F | 66°F | 54°F | 4.3" |
| November | 32°F | 52°F | 41°F | 2.7" |
| December | 20°F | 37°F | 28°F | 3.3" |
| Index | Hamilton | Iowa | National |
| Air quality index | 39 | 39 | 42 |
| Pollution index | 1,478,700 | 1,154,535 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 306 |
| Days with moderate air quality | 59 |
| Days w/ poor A.Q. for sensitive groups | 0 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.010% |
| Carbon Tetrachloride | 0.002% |
| Lead | 0.010% |
| Mercury | 0.010% |
| City | Population | Air Quality Index | National Avg. |
| Blakesburg, IA | 232 | 39 | 22.0% |
| Harvey, IA | 176 | 39 | 22.0% |
| Oskaloosa, IA | 11,727 | 39 | 22.0% |
| Melrose, IA | 179 | 39 | 22.0% |
| Knoxville, IA | 7,154 | 39 | 22.0% |
| Hamilton, IA | 61 | 39 | 22.0% |
| City | Population | Air Quality Index | National Avg. |
| Klukwan, AK | 61 | 20 | 60.0% |
| Jennette, AR | 61 | 45 | 10.0% |
| Yucca, AZ | 61 | 13 | 74.0% |
| Mount Hebron, CA | 61 | 29 | 42.0% |
| Rodriguez Camp, CA | 61 | 67 | 34.0% |
| Hamilton, IA | 61 | 39 | 22.0% |
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