Belknap, Illinois has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 47.4 °F (low) to 67.6 °F (high). Annual precipitation averages 50 Inches. Belknap is located in USDA Plant Hardiness Zone 7a. The growing season typically runs from the last frost around Mar. 21 - Mar. 31 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 25.9 °F | 42.9 °F | 3.83 in. |
| February | 28.9 °F | 47.4 °F | 3.52 in. |
| March | 36.9 °F | 57.0 °F | 4.69 in. |
| April | 46.8 °F | 68.5 °F | 5.29 in. |
| May | 56.9 °F | 77.0 °F | 5.3 in. |
| June | 65.3 °F | 85.4 °F | 4.54 in. |
| July | 68.9 °F | 88.4 °F | 4.01 in. |
| August | 66.6 °F | 87.5 °F | 2.93 in. |
| September | 58.6 °F | 81.8 °F | 3.43 in. |
| October | 47.0 °F | 71.0 °F | 3.83 in. |
| November | 37.1 °F | 57.3 °F | 4.33 in. |
| December | 29.7 °F | 46.4 °F | 4.29 in. |
| Annual | 47.4 °F | 67.6 °F | 49.99 in. |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Mar. 21 - Mar. 31 |
| Average Days With Frost | 50-75 Days |
| Plant Hardiness Zone | Zone 7a : 0°F to 5°F |
| Plant Hardiness Zone - 2012 | Zone 6b : -5°F to 0°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |