Colwell, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 36 °F (low) to 55.6 °F (high). Annual precipitation averages 37.7 Inches. Colwell is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 7.5 °F | 24.3 °F | 0.99 in. |
| February | 11.5 °F | 28.5 °F | 1.11 in. |
| March | 23.4 °F | 41.4 °F | 1.92 in. |
| April | 35.3 °F | 57.1 °F | 3.81 in. |
| May | 47.5 °F | 69.1 °F | 5.08 in. |
| June | 58.1 °F | 78.6 °F | 6.15 in. |
| July | 61.4 °F | 81.6 °F | 4.71 in. |
| August | 58.7 °F | 79.5 °F | 4.25 in. |
| September | 50.3 °F | 73.6 °F | 3.74 in. |
| October | 37.8 °F | 60.2 °F | 2.75 in. |
| November | 25.7 °F | 43.4 °F | 1.75 in. |
| December | 14.4 °F | 29.9 °F | 1.4 in. |
| Annual | 36 °F | 55.6 °F | 37.66 in. |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 5a : -20°F to -15°F |
| Plant Hardiness Zone - 2012 | Zone 5a : -20°F to -15°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |