Plainfield, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 2.9 °C (low) to 13.9 °C (high). Annual precipitation averages 950 Millimeters. Plainfield is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -12.8 °C | -3.4 °C | 26.16 mm |
| February | -10.6 °C | -1.1 °C | 28.96 mm |
| March | -4 °C | 6.3 °C | 49.53 mm |
| April | 2.4 °C | 14.7 °C | 98.55 mm |
| May | 9.3 °C | 21.4 °C | 126.75 mm |
| June | 15.3 °C | 26.7 °C | 151.38 mm |
| July | 17.1 °C | 28.3 °C | 117.86 mm |
| August | 15.6 °C | 27.2 °C | 108.46 mm |
| September | 10.8 °C | 23.9 °C | 92.46 mm |
| October | 3.9 °C | 16.4 °C | 66.8 mm |
| November | -2.9 °C | 7.2 °C | 45.97 mm |
| December | -9.1 °C | -0.3 °C | 37.08 mm |
| Annual | 2.9 °C | 13.9 °C | 949.96 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 5a : -28.9°C to -26.1°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 |