Delaware, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 35.8 °F (low) to 56.2 °F (high). Annual precipitation averages 39.7 Inches. Delaware is located in USDA Plant Hardiness Zone 4b. 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 | 8.0 °F | 25.6 °F | 1.25 in. |
| February | 11.8 °F | 30.1 °F | 1.32 in. |
| March | 23.7 °F | 43.3 °F | 2.14 in. |
| April | 34.8 °F | 57.1 °F | 4.0 in. |
| May | 46.9 °F | 68.7 °F | 4.79 in. |
| June | 57.6 °F | 78.7 °F | 6.01 in. |
| July | 60.7 °F | 81.4 °F | 4.76 in. |
| August | 58.2 °F | 79.7 °F | 4.49 in. |
| September | 49.5 °F | 73.6 °F | 3.9 in. |
| October | 37.3 °F | 60.4 °F | 3.04 in. |
| November | 25.6 °F | 44.7 °F | 2.3 in. |
| December | 15.0 °F | 31.5 °F | 1.68 in. |
| Annual | 35.8 °F | 56.2 °F | 39.68 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 4b : -25°F to -20°F |
| Plant Hardiness Zone - 2012 | Zone 5a : -20°F to -15°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |