Hamilton, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 40.2 °F (low) to 60.3 °F (high). Annual precipitation averages 37.2 Inches. Hamilton is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 13.2 °F | 30.7 °F | 1.13 in. |
| February | 17.0 °F | 35.4 °F | 1.49 in. |
| March | 27.8 °F | 48.8 °F | 2.14 in. |
| April | 39.3 °F | 61.6 °F | 3.86 in. |
| May | 51.3 °F | 71.5 °F | 5.18 in. |
| June | 61.5 °F | 81.3 °F | 5.18 in. |
| July | 65.1 °F | 85.2 °F | 4.25 in. |
| August | 62.7 °F | 83.3 °F | 4.16 in. |
| September | 53.9 °F | 76.4 °F | 3.61 in. |
| October | 41.7 °F | 63.9 °F | 2.65 in. |
| November | 29.7 °F | 48.6 °F | 2.08 in. |
| December | 19.1 °F | 36.3 °F | 1.43 in. |
| Annual | 40.2 °F | 60.3 °F | 37.16 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 5b : -15°F to -10°F |
| Plant Hardiness Zone - 2012 | Zone 5b : -15°F to -10°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |