Williamsfield, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.6 °C (low) to 15.9 °C (high). Annual precipitation averages 961.4 Millimeters. Williamsfield 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 | -9.7 °C | -0.4 °C | 47.75 mm |
| February | -7.8 °C | 2.1 °C | 49.78 mm |
| March | -2.1 °C | 9.3 °C | 62.74 mm |
| April | 3.8 °C | 16.7 °C | 94.49 mm |
| May | 10.5 °C | 22.6 °C | 128.27 mm |
| June | 15.9 °C | 27.5 °C | 117.86 mm |
| July | 17.7 °C | 29.1 °C | 97.28 mm |
| August | 16.5 °C | 28.3 °C | 89.92 mm |
| September | 11.9 °C | 25.1 °C | 86.11 mm |
| October | 5.4 °C | 18.1 °C | 74.17 mm |
| November | -0.9 °C | 9.7 °C | 62.74 mm |
| December | -6.4 °C | 2.6 °C | 50.29 mm |
| Annual | 4.6 °C | 15.9 °C | 961.4 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 5b : -26.1°C to -23.3°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |