Union, West Virginia has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 40.4 °F (low) to 63.7 °F (high). Annual precipitation averages 39.2 Inches. Union is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 21.9 °F | 41.7 °F | 2.65 in. |
| February | 23.7 °F | 44.9 °F | 2.29 in. |
| March | 29.6 °F | 53.7 °F | 3.35 in. |
| April | 38.7 °F | 65.1 °F | 3.53 in. |
| May | 48.1 °F | 72.9 °F | 4.46 in. |
| June | 56.2 °F | 79.4 °F | 4.23 in. |
| July | 60.3 °F | 82.9 °F | 3.72 in. |
| August | 59.0 °F | 81.8 °F | 3.63 in. |
| September | 52.0 °F | 76.2 °F | 3.38 in. |
| October | 39.7 °F | 66.2 °F | 2.6 in. |
| November | 30.2 °F | 54.4 °F | 2.45 in. |
| December | 24.9 °F | 44.8 °F | 2.9 in. |
| Annual | 40.4 °F | 63.7 °F | 39.19 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6b : -5°F to 0°F |
| Plant Hardiness Zone - 2012 | Zone 6b : -5°F to 0°F |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |