Derby, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 39.8 °F (low) to 60.4 °F (high). Annual precipitation averages 38.2 Inches. Derby is located in USDA Plant Hardiness Zone 5b. 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 | 13.2 °F | 31.5 °F | 1.03 in. |
| February | 17.1 °F | 36.1 °F | 1.38 in. |
| March | 27.8 °F | 49.0 °F | 2.17 in. |
| April | 38.7 °F | 61.5 °F | 3.98 in. |
| May | 50.6 °F | 71.3 °F | 5.42 in. |
| June | 60.6 °F | 80.7 °F | 5.26 in. |
| July | 64.9 °F | 85.1 °F | 4.49 in. |
| August | 62.2 °F | 83.3 °F | 4.39 in. |
| September | 53.2 °F | 76.5 °F | 3.76 in. |
| October | 41.2 °F | 64.0 °F | 2.88 in. |
| November | 29.1 °F | 49.0 °F | 2.03 in. |
| December | 18.9 °F | 36.7 °F | 1.44 in. |
| Annual | 39.8 °F | 60.4 °F | 38.23 in. |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| 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 |