Greenfield, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.2 °C (low) to 15.7 °C (high). Annual precipitation averages 902.2 Millimeters. Greenfield is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -10.7 °C | -0.6 °C | 21.84 mm |
| February | -8.4 °C | 2.3 °C | 31.24 mm |
| March | -2.6 °C | 9.4 °C | 52.07 mm |
| April | 3.6 °C | 16.4 °C | 95 mm |
| May | 10.2 °C | 22.1 °C | 127 mm |
| June | 15.8 °C | 27.3 °C | 122.94 mm |
| July | 18.1 °C | 29.4 °C | 101.85 mm |
| August | 16.8 °C | 28.5 °C | 99.31 mm |
| September | 11.9 °C | 24.9 °C | 96.27 mm |
| October | 5 °C | 17.9 °C | 71.63 mm |
| November | -1.8 °C | 9.3 °C | 47.75 mm |
| December | -7.7 °C | 2 °C | 35.31 mm |
| Annual | 4.2 °C | 15.7 °C | 902.21 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| 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 |