Greenfield, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 39.5 °F (low) to 60.3 °F (high). Annual precipitation averages 35.5 Inches. 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 | 12.8 °F | 30.9 °F | 0.86 in. |
| February | 16.8 °F | 36.1 °F | 1.23 in. |
| March | 27.4 °F | 48.9 °F | 2.05 in. |
| April | 38.4 °F | 61.6 °F | 3.74 in. |
| May | 50.4 °F | 71.7 °F | 5.0 in. |
| June | 60.5 °F | 81.2 °F | 4.84 in. |
| July | 64.5 °F | 84.9 °F | 4.01 in. |
| August | 62.2 °F | 83.3 °F | 3.91 in. |
| September | 53.5 °F | 76.9 °F | 3.79 in. |
| October | 41.0 °F | 64.2 °F | 2.82 in. |
| November | 28.7 °F | 48.7 °F | 1.88 in. |
| December | 18.2 °F | 35.6 °F | 1.39 in. |
| Annual | 39.5 °F | 60.3 °F | 35.52 in. |
| 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 : -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 |