Plainfield, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 37.3 °F (low) to 57.1 °F (high). Annual precipitation averages 37.4 Inches. 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 | 8.9 °F | 25.8 °F | 1.03 in. |
| February | 12.9 °F | 30.1 °F | 1.14 in. |
| March | 24.8 °F | 43.3 °F | 1.95 in. |
| April | 36.4 °F | 58.5 °F | 3.88 in. |
| May | 48.7 °F | 70.5 °F | 4.99 in. |
| June | 59.5 °F | 80.1 °F | 5.96 in. |
| July | 62.7 °F | 83.0 °F | 4.64 in. |
| August | 60.0 °F | 80.9 °F | 4.27 in. |
| September | 51.5 °F | 75.0 °F | 3.64 in. |
| October | 39.1 °F | 61.6 °F | 2.63 in. |
| November | 26.8 °F | 44.9 °F | 1.81 in. |
| December | 15.7 °F | 31.4 °F | 1.46 in. |
| Annual | 37.3 °F | 57.1 °F | 37.4 in. |
| 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 : -20°F to -15°F |
| Plant Hardiness Zone - 2012 | Zone 5a : -20°F to -15°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |