Mascoutah, Illinois has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 46 °F (low) to 66.2 °F (high). Annual precipitation averages 44.1 Inches. Mascoutah is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 22.6 °F | 39.8 °F | 2.81 in. |
| February | 25.8 °F | 45.1 °F | 2.42 in. |
| March | 34.6 °F | 55.3 °F | 3.47 in. |
| April | 45.5 °F | 67.1 °F | 4.98 in. |
| May | 56.3 °F | 76.1 °F | 5.15 in. |
| June | 65.1 °F | 85.1 °F | 4.89 in. |
| July | 68.8 °F | 88.5 °F | 3.94 in. |
| August | 66.7 °F | 87.4 °F | 3.27 in. |
| September | 58.0 °F | 80.9 °F | 3.42 in. |
| October | 46.3 °F | 69.6 °F | 3.13 in. |
| November | 35.4 °F | 55.3 °F | 3.79 in. |
| December | 26.9 °F | 44.1 °F | 2.85 in. |
| Annual | 46 °F | 66.2 °F | 44.12 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 6b : -5°F to 0°F |
| Plant Hardiness Zone - 2012 | Zone 6b : -5°F to 0°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |