Union City, Tennessee has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 8.9 °C (low) to 20.5 °C (high). Annual precipitation averages 1357.6 Millimeters. Union City is located in USDA Plant Hardiness Zone 7b. The growing season typically runs from the last frost around Mar. 21 - Mar. 31 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -2.7 °C | 7.2 °C | 101.35 mm |
| February | -1.1 °C | 9.7 °C | 114.55 mm |
| March | 3.4 °C | 15.1 °C | 130.81 mm |
| April | 8.5 °C | 20.9 °C | 132.08 mm |
| May | 14.4 °C | 25.8 °C | 145.03 mm |
| June | 18.8 °C | 30.1 °C | 110.74 mm |
| July | 20.7 °C | 31.7 °C | 104.65 mm |
| August | 19.3 °C | 31.3 °C | 80.77 mm |
| September | 14.9 °C | 28.2 °C | 95 mm |
| October | 8.3 °C | 22.3 °C | 99.82 mm |
| November | 2.8 °C | 14.9 °C | 112.01 mm |
| December | -1 °C | 9.1 °C | 130.81 mm |
| Annual | 8.9 °C | 20.5 °C | 1357.62 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Mar. 21 - Mar. 31 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 7b : -15°C to -12.2°C |
| Plant Hardiness Zone - 2012 | Zone 7a : -17.8°C to -15°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |