Delaware, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 2.1 °C (low) to 13.5 °C (high). Annual precipitation averages 1007.9 Millimeters. 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 | -13.3 °C | -3.6 °C | 31.75 mm |
| February | -11.2 °C | -1.1 °C | 33.53 mm |
| March | -4.6 °C | 6.3 °C | 54.36 mm |
| April | 1.6 °C | 13.9 °C | 101.6 mm |
| May | 8.3 °C | 20.4 °C | 121.67 mm |
| June | 14.2 °C | 25.9 °C | 152.65 mm |
| July | 15.9 °C | 27.4 °C | 120.9 mm |
| August | 14.6 °C | 26.5 °C | 114.05 mm |
| September | 9.7 °C | 23.1 °C | 99.06 mm |
| October | 2.9 °C | 15.8 °C | 77.22 mm |
| November | -3.6 °C | 7.1 °C | 58.42 mm |
| December | -9.4 °C | -0.3 °C | 42.67 mm |
| Annual | 2.1 °C | 13.5 °C | 1007.88 mm |
| 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 : -31.7°C to -28.9°C |
| Plant Hardiness Zone - 2012 | Zone 5a : -28.9°C to -26.1°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |