Karns, Tennessee has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 9.1 °C (low) to 20.9 °C (high). Annual precipitation averages 1432.3 Millimeters. Karns is located in USDA Plant Hardiness Zone 7b. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -1.8 °C | 8.5 °C | 129.29 mm |
| February | -0.2 °C | 11.1 °C | 132.08 mm |
| March | 3.4 °C | 16.1 °C | 132.33 mm |
| April | 8.2 °C | 21.6 °C | 133.1 mm |
| May | 13.4 °C | 25.9 °C | 109.47 mm |
| June | 17.8 °C | 29.5 °C | 120.14 mm |
| July | 20.1 °C | 31.1 °C | 151.38 mm |
| August | 19.4 °C | 30.8 °C | 88.65 mm |
| September | 16 °C | 28.2 °C | 103.89 mm |
| October | 9.2 °C | 22.1 °C | 83.82 mm |
| November | 3.1 °C | 15.4 °C | 104.14 mm |
| December | 0.1 °C | 10.2 °C | 144.02 mm |
| Annual | 9.1 °C | 20.9 °C | 1432.31 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| 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 |