Delta, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.3 °C (low) to 15.5 °C (high). Annual precipitation averages 960.9 Millimeters. Delta 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 | -10.4 °C | -0.9 °C | 30.23 mm |
| February | -8.4 °C | 1.7 °C | 37.85 mm |
| March | -2.4 °C | 8.8 °C | 56.39 mm |
| April | 3.7 °C | 16.3 °C | 97.28 mm |
| May | 10.4 °C | 21.9 °C | 128.27 mm |
| June | 16.2 °C | 27.4 °C | 136.65 mm |
| July | 18 °C | 29.4 °C | 106.68 mm |
| August | 16.7 °C | 28.3 °C | 109.73 mm |
| September | 11.7 °C | 24.7 °C | 92.96 mm |
| October | 5.1 °C | 17.7 °C | 69.85 mm |
| November | -1.4 °C | 9.1 °C | 55.63 mm |
| December | -7.1 °C | 2 °C | 39.37 mm |
| Annual | 4.3 °C | 15.5 °C | 960.89 mm |
| 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 : -26.1°C to -23.3°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |