Cairo, Illinois has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 48.1 °F (low) to 68.2 °F (high). Annual precipitation averages 50.3 Inches. Cairo 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 | 27.0 °F | 43.3 °F | 3.95 in. |
| February | 29.8 °F | 48.3 °F | 3.91 in. |
| March | 37.7 °F | 58.1 °F | 4.97 in. |
| April | 47.7 °F | 69.4 °F | 5.18 in. |
| May | 58.1 °F | 78.4 °F | 5.3 in. |
| June | 66.4 °F | 86.5 °F | 4.18 in. |
| July | 69.8 °F | 89.1 °F | 3.94 in. |
| August | 67.2 °F | 87.8 °F | 2.85 in. |
| September | 59.0 °F | 82.1 °F | 3.44 in. |
| October | 47.2 °F | 71.4 °F | 3.93 in. |
| November | 37.3 °F | 57.7 °F | 4.29 in. |
| December | 30.3 °F | 46.7 °F | 4.33 in. |
| Annual | 48.1 °F | 68.2 °F | 50.27 in. |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Mar. 21 - Mar. 31 |
| Average Days With Frost | 75-100 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 |