Union, South Carolina has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 49.3 °F (low) to 73 °F (high). Annual precipitation averages 45.6 Inches. Union is located in USDA Plant Hardiness Zone 8a. 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 | 30.8 °F | 53.5 °F | 4.05 in. |
| February | 33.2 °F | 57.3 °F | 3.61 in. |
| March | 39.2 °F | 65.1 °F | 4.28 in. |
| April | 47.5 °F | 74.2 °F | 3.66 in. |
| May | 56.9 °F | 81.1 °F | 3.37 in. |
| June | 65.3 °F | 87.7 °F | 4.26 in. |
| July | 69.0 °F | 91.1 °F | 3.61 in. |
| August | 67.8 °F | 89.2 °F | 4.07 in. |
| September | 61.6 °F | 83.7 °F | 3.77 in. |
| October | 49.0 °F | 74.0 °F | 3.26 in. |
| November | 38.2 °F | 63.7 °F | 3.52 in. |
| December | 33.3 °F | 55.8 °F | 4.16 in. |
| Annual | 49.3 °F | 73 °F | 45.62 in. |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| 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 | Moderate Drought |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |