Karnak, Illinois has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 47.9 °F (low) to 67.6 °F (high). Annual precipitation averages 49.8 Inches. Karnak 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 Nov. 1 - Nov. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 26.4 °F | 42.9 °F | 3.83 in. |
| February | 29.4 °F | 47.6 °F | 3.55 in. |
| March | 37.3 °F | 57.3 °F | 4.7 in. |
| April | 47.3 °F | 68.3 °F | 5.26 in. |
| May | 57.3 °F | 77.0 °F | 5.27 in. |
| June | 65.7 °F | 85.4 °F | 4.52 in. |
| July | 69.3 °F | 88.5 °F | 3.96 in. |
| August | 67.1 °F | 87.4 °F | 2.84 in. |
| September | 59.3 °F | 81.8 °F | 3.43 in. |
| October | 47.7 °F | 71.0 °F | 3.85 in. |
| November | 37.4 °F | 57.3 °F | 4.28 in. |
| December | 30.2 °F | 46.4 °F | 4.3 in. |
| Annual | 47.9 °F | 67.6 °F | 49.79 in. |
| Average First Frost Date | Nov. 1 - Nov. 10 |
| 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 7a : 0°F to 5°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |