Union, Louisiana has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 58.4 °F (low) to 78.4 °F (high). Annual precipitation averages 64.9 Inches. Union is located in USDA Plant Hardiness Zone 9a. The growing season typically runs from the last frost around Feb. 1 - Feb. 10 through the first frost around Dec. 11 - Dec. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 42.1 °F | 62.4 °F | 5.8 in. |
| February | 45.5 °F | 66.2 °F | 4.44 in. |
| March | 51.4 °F | 72.5 °F | 4.29 in. |
| April | 57.2 °F | 78.2 °F | 5.14 in. |
| May | 65.3 °F | 84.8 °F | 6.13 in. |
| June | 71.6 °F | 89.4 °F | 7.22 in. |
| July | 73.7 °F | 91.0 °F | 6.32 in. |
| August | 73.2 °F | 91.4 °F | 6.98 in. |
| September | 69.4 °F | 88.1 °F | 5.19 in. |
| October | 58.8 °F | 80.7 °F | 4.4 in. |
| November | 48.7 °F | 71.2 °F | 4.15 in. |
| December | 43.9 °F | 64.7 °F | 4.86 in. |
| Annual | 58.4 °F | 78.4 °F | 64.92 in. |
| Average First Frost Date | Dec. 11 - Dec. 20 |
| Average Last Frost Date | Feb. 1 - Feb. 10 |
| Average Days With Frost | 10-20 Days |
| Plant Hardiness Zone | Zone 9a : 20°F to 25°F |
| Plant Hardiness Zone - 2012 | Zone 9a : 20°F to 25°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |