Union, Louisiana has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 14.7 °C (low) to 25.8 °C (high). Annual precipitation averages 1649 Millimeters. 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 | 5.6 °C | 16.9 °C | 147.32 mm |
| February | 7.5 °C | 19 °C | 112.78 mm |
| March | 10.8 °C | 22.5 °C | 108.97 mm |
| April | 14 °C | 25.7 °C | 130.56 mm |
| May | 18.5 °C | 29.3 °C | 155.7 mm |
| June | 22 °C | 31.9 °C | 183.39 mm |
| July | 23.2 °C | 32.8 °C | 160.53 mm |
| August | 22.9 °C | 33 °C | 177.29 mm |
| September | 20.8 °C | 31.2 °C | 131.83 mm |
| October | 14.9 °C | 27.1 °C | 111.76 mm |
| November | 9.3 °C | 21.8 °C | 105.41 mm |
| December | 6.6 °C | 18.2 °C | 123.44 mm |
| Annual | 14.7 °C | 25.8 °C | 1648.98 mm |
| 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 : -6.7°C to -3.9°C |
| Plant Hardiness Zone - 2012 | Zone 9a : -6.7°C to -3.9°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |