Gilson, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 4.7 °C (low) to 16 °C (high). Annual precipitation averages 982.7 Millimeters. Gilson 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 | -9.6 °C | -0.2 °C | 47.24 mm |
| February | -7.7 °C | 2.3 °C | 50.29 mm |
| March | -1.9 °C | 9.5 °C | 62.99 mm |
| April | 3.9 °C | 16.7 °C | 97.03 mm |
| May | 10.7 °C | 22.6 °C | 130.3 mm |
| June | 16.1 °C | 27.5 °C | 119.63 mm |
| July | 17.9 °C | 29.2 °C | 101.09 mm |
| August | 16.7 °C | 28.3 °C | 91.69 mm |
| September | 12.1 °C | 25.1 °C | 94.49 mm |
| October | 5.4 °C | 18.2 °C | 74.17 mm |
| November | -0.8 °C | 9.7 °C | 62.74 mm |
| December | -6.3 °C | 2.8 °C | 51.05 mm |
| Annual | 4.7 °C | 16 °C | 982.71 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 |