Gilman, 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 61.3 °F (high). Annual precipitation averages 39 Inches. Gilman is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 16.1 °F | 32.3 °F | 2.24 in. |
| February | 19.3 °F | 36.9 °F | 1.93 in. |
| March | 28.8 °F | 49.0 °F | 2.58 in. |
| April | 38.9 °F | 62.5 °F | 3.81 in. |
| May | 50.5 °F | 73.5 °F | 4.49 in. |
| June | 60.3 °F | 82.2 °F | 4.63 in. |
| July | 63.6 °F | 84.8 °F | 4.44 in. |
| August | 61.3 °F | 83.2 °F | 3.63 in. |
| September | 53.2 °F | 78.5 °F | 3.06 in. |
| October | 42.0 °F | 65.7 °F | 3.3 in. |
| November | 31.4 °F | 50.1 °F | 2.75 in. |
| December | 21.8 °F | 37.4 °F | 2.15 in. |
| Annual | 40.6 °F | 61.3 °F | 39.01 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 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 |