Union, Mississippi has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 52.4 °F (low) to 75.7 °F (high). Annual precipitation averages 59.8 Inches. Union is located in USDA Plant Hardiness Zone 8b. The growing season typically runs from the last frost around Mar. 21 - Mar. 31 through the first frost around Nov. 1 - Nov. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 34.8 °F | 56.5 °F | 5.96 in. |
| February | 37.9 °F | 61.1 °F | 5.7 in. |
| March | 44.1 °F | 68.8 °F | 5.77 in. |
| April | 51.1 °F | 76.0 °F | 6.15 in. |
| May | 59.9 °F | 82.9 °F | 4.28 in. |
| June | 67.5 °F | 89.6 °F | 4.52 in. |
| July | 70.2 °F | 91.7 °F | 5.46 in. |
| August | 69.2 °F | 91.3 °F | 4.56 in. |
| September | 63.6 °F | 87.3 °F | 3.53 in. |
| October | 52.1 °F | 77.9 °F | 3.68 in. |
| November | 41.7 °F | 66.7 °F | 4.64 in. |
| December | 36.9 °F | 58.8 °F | 5.55 in. |
| Annual | 52.4 °F | 75.7 °F | 59.8 in. |
| Average First Frost Date | Nov. 1 - Nov. 10 |
| Average Last Frost Date | Mar. 21 - Mar. 31 |
| Average Days With Frost | 40-50 Days |
| Plant Hardiness Zone | Zone 8b : 15°F to 20°F |
| Plant Hardiness Zone - 2012 | Zone 8a : 10°F to 15°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |