Mercer, Tennessee has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 49.8 °F (low) to 70.6 °F (high). Annual precipitation averages 56 Inches. Mercer is located in USDA Plant Hardiness Zone 8a. 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 | 29.4 °F | 47.3 °F | 4.28 in. |
| February | 32.7 °F | 52.3 °F | 4.97 in. |
| March | 40.1 °F | 61.1 °F | 5.65 in. |
| April | 49.0 °F | 71.8 °F | 5.43 in. |
| May | 58.8 °F | 79.6 °F | 5.51 in. |
| June | 66.9 °F | 86.9 °F | 4.55 in. |
| July | 70.2 °F | 89.8 °F | 4.34 in. |
| August | 68.3 °F | 89.3 °F | 3.48 in. |
| September | 61.2 °F | 83.8 °F | 3.99 in. |
| October | 49.0 °F | 73.5 °F | 3.95 in. |
| November | 39.0 °F | 61.1 °F | 4.39 in. |
| December | 32.5 °F | 50.6 °F | 5.49 in. |
| Annual | 49.8 °F | 70.6 °F | 56.03 in. |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Mar. 21 - Mar. 31 |
| Average Days With Frost | 50-75 Days |
| Plant Hardiness Zone | Zone 8a : 10°F to 15°F |
| Plant Hardiness Zone - 2012 | Zone 7b : 5°F to 10°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |