Old Shawneetown, Illinois has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 47.1 °F (low) to 67.1 °F (high). Annual precipitation averages 46.6 Inches. Old Shawneetown is located in USDA Plant Hardiness Zone 7a. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 25.6 °F | 41.5 °F | 3.57 in. |
| February | 28.2 °F | 46.4 °F | 3.26 in. |
| March | 36.2 °F | 56.0 °F | 4.67 in. |
| April | 46.3 °F | 67.9 °F | 4.69 in. |
| May | 57.0 °F | 77.0 °F | 5.05 in. |
| June | 65.3 °F | 85.5 °F | 4.1 in. |
| July | 68.5 °F | 88.4 °F | 4.17 in. |
| August | 66.2 °F | 87.2 °F | 3.01 in. |
| September | 58.7 °F | 82.2 °F | 3.02 in. |
| October | 47.1 °F | 70.6 °F | 3.21 in. |
| November | 36.5 °F | 56.5 °F | 3.99 in. |
| December | 29.2 °F | 45.8 °F | 3.86 in. |
| Annual | 47.1 °F | 67.1 °F | 46.6 in. |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 75-100 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 | Normal |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |