Union, Alabama has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 11.7 °C (low) to 23.7 °C (high). Annual precipitation averages 1406.1 Millimeters. Union is located in USDA Plant Hardiness Zone 8b. The growing season typically runs from the last frost around Mar. 11 - Mar. 20 through the first frost around Nov. 1 - Nov. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 1.5 °C | 12.8 °C | 137.41 mm |
| February | 3.3 °C | 15.4 °C | 138.43 mm |
| March | 6.6 °C | 20.1 °C | 134.87 mm |
| April | 10.6 °C | 23.9 °C | 133.35 mm |
| May | 15.7 °C | 27.9 °C | 98.04 mm |
| June | 20.4 °C | 31.4 °C | 113.54 mm |
| July | 22.2 °C | 32.6 °C | 124.21 mm |
| August | 21.3 °C | 32.5 °C | 110.74 mm |
| September | 18.2 °C | 30.4 °C | 91.19 mm |
| October | 11.6 °C | 25.1 °C | 86.61 mm |
| November | 5.7 °C | 18.8 °C | 110.74 mm |
| December | 2.7 °C | 14 °C | 127 mm |
| Annual | 11.7 °C | 23.7 °C | 1406.13 mm |
| Average First Frost Date | Nov. 1 - Nov. 10 |
| Average Last Frost Date | Mar. 11 - Mar. 20 |
| Average Days With Frost | 50-75 Days |
| Plant Hardiness Zone | Zone 8b : -9.4°C to -6.7°C |
| Plant Hardiness Zone - 2012 | Zone 8a : -12.2°C to -9.4°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |