Anna, Illinois has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 46.5 °F (low) to 67 °F (high). Annual precipitation averages 50.6 Inches. Anna 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 | 24.6 °F | 42.0 °F | 3.7 in. |
| February | 27.6 °F | 47.1 °F | 3.29 in. |
| March | 36.2 °F | 56.9 °F | 4.74 in. |
| April | 46.1 °F | 68.1 °F | 5.46 in. |
| May | 55.9 °F | 76.4 °F | 5.72 in. |
| June | 64.2 °F | 85.0 °F | 4.72 in. |
| July | 68.2 °F | 87.4 °F | 3.93 in. |
| August | 65.9 °F | 87.3 °F | 3.12 in. |
| September | 58.0 °F | 81.5 °F | 3.49 in. |
| October | 46.6 °F | 70.5 °F | 3.77 in. |
| November | 36.7 °F | 56.8 °F | 4.65 in. |
| December | 28.2 °F | 45.4 °F | 4.04 in. |
| Annual | 46.5 °F | 67 °F | 50.63 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 | Cfa - Humid Subtropical Climate |