Grand Tower, Illinois has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 46.7 °F (low) to 67.5 °F (high). Annual precipitation averages 45.8 Inches. Grand Tower 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 | 24.2 °F | 41.6 °F | 2.97 in. |
| February | 28.3 °F | 46.7 °F | 3.03 in. |
| March | 35.8 °F | 56.8 °F | 4.31 in. |
| April | 46.2 °F | 68.1 °F | 5.23 in. |
| May | 56.6 °F | 77.2 °F | 5.15 in. |
| June | 65.6 °F | 86.1 °F | 4.52 in. |
| July | 69.1 °F | 89.2 °F | 3.55 in. |
| August | 66.4 °F | 87.8 °F | 2.96 in. |
| September | 57.9 °F | 82.6 °F | 2.99 in. |
| October | 45.8 °F | 71.1 °F | 3.39 in. |
| November | 36.5 °F | 56.9 °F | 4.33 in. |
| December | 28.3 °F | 45.5 °F | 3.4 in. |
| Annual | 46.7 °F | 67.5 °F | 45.83 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 | Moderate Drought |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |