Union, Ohio has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 43 °F (low) to 62.1 °F (high). Annual precipitation averages 41.1 Inches. Union is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 20.4 °F | 35.9 °F | 3.04 in. |
| February | 22.6 °F | 39.7 °F | 2.3 in. |
| March | 30.9 °F | 49.9 °F | 3.3 in. |
| April | 41.7 °F | 62.7 °F | 4.22 in. |
| May | 52.8 °F | 72.9 °F | 4.53 in. |
| June | 61.7 °F | 81.4 °F | 4.36 in. |
| July | 64.7 °F | 84.5 °F | 4.11 in. |
| August | 62.8 °F | 83.6 °F | 3.02 in. |
| September | 55.3 °F | 77.6 °F | 3.19 in. |
| October | 43.8 °F | 65.3 °F | 2.87 in. |
| November | 33.5 °F | 51.7 °F | 3.06 in. |
| December | 25.7 °F | 40.4 °F | 3.08 in. |
| Annual | 43 °F | 62.1 °F | 41.08 in. |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 6b : -5°F to 0°F |
| Plant Hardiness Zone - 2012 | Zone 6a : -10°F to -5°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |