Tamms, Illinois has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 47.7 °F (low) to 68.1 °F (high). Annual precipitation averages 49.9 Inches. Tamms 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 | 26.3 °F | 43.1 °F | 3.73 in. |
| February | 29.4 °F | 48.4 °F | 3.67 in. |
| March | 37.4 °F | 58.1 °F | 4.73 in. |
| April | 47.1 °F | 68.9 °F | 5.55 in. |
| May | 57.5 °F | 77.7 °F | 5.15 in. |
| June | 65.8 °F | 86.0 °F | 4.42 in. |
| July | 69.3 °F | 88.9 °F | 3.66 in. |
| August | 66.9 °F | 87.8 °F | 3.01 in. |
| September | 58.8 °F | 82.0 °F | 3.41 in. |
| October | 47.2 °F | 71.6 °F | 3.93 in. |
| November | 37.0 °F | 57.7 °F | 4.58 in. |
| December | 29.9 °F | 46.7 °F | 4.06 in. |
| Annual | 47.7 °F | 68.1 °F | 49.9 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 6b : -5°F to 0°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |