Greenfield, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 6.4 °C (low) to 17.6 °C (high). Annual precipitation averages 1020.6 Millimeters. Greenfield is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -6.9 °C | 2.3 °C | 55.88 mm |
| February | -4.9 °C | 5.2 °C | 51.82 mm |
| March | 0 °C | 11.4 °C | 78.99 mm |
| April | 5.8 °C | 18.2 °C | 110.24 mm |
| May | 12.2 °C | 23.7 °C | 123.95 mm |
| June | 17.2 °C | 28.4 °C | 115.57 mm |
| July | 19.1 °C | 30.1 °C | 93.73 mm |
| August | 17.7 °C | 29.6 °C | 82.3 mm |
| September | 13.1 °C | 26.4 °C | 81.79 mm |
| October | 6.7 °C | 19.6 °C | 82.8 mm |
| November | 0.8 °C | 11.7 °C | 85.6 mm |
| December | -4.2 °C | 5 °C | 57.91 mm |
| Annual | 6.4 °C | 17.6 °C | 1020.58 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 6a : -23.3°C to -20.6°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |