Plainfield, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 40.6 °F (low) to 60.1 °F (high). Annual precipitation averages 40 Inches. Plainfield is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 15.9 °F | 31.5 °F | 2.13 in. |
| February | 18.7 °F | 35.4 °F | 1.96 in. |
| March | 28.4 °F | 47.4 °F | 2.52 in. |
| April | 38.9 °F | 60.5 °F | 4.01 in. |
| May | 49.8 °F | 71.4 °F | 4.79 in. |
| June | 59.9 °F | 80.9 °F | 4.69 in. |
| July | 63.7 °F | 84.4 °F | 4.21 in. |
| August | 62.2 °F | 82.6 °F | 4.2 in. |
| September | 54.4 °F | 77.0 °F | 3.35 in. |
| October | 42.3 °F | 63.9 °F | 3.44 in. |
| November | 31.6 °F | 49.2 °F | 2.51 in. |
| December | 21.8 °F | 36.7 °F | 2.23 in. |
| Annual | 40.6 °F | 60.1 °F | 40.04 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 100-125 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 |