Killen, Alabama has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 9.6 °C (low) to 22 °C (high). Annual precipitation averages 1491.5 Millimeters. Killen is located in USDA Plant Hardiness Zone 8a. The growing season typically runs from the last frost around Mar. 21 - Mar. 31 through the first frost around Nov. 1 - Nov. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -1.1 °C | 10.3 °C | 135.38 mm |
| February | 0.7 °C | 12.7 °C | 138.18 mm |
| March | 4.5 °C | 17.5 °C | 144.27 mm |
| April | 9.1 °C | 22.5 °C | 126.49 mm |
| May | 14.1 °C | 26.5 °C | 129.29 mm |
| June | 18.6 °C | 30.3 °C | 117.09 mm |
| July | 20.4 °C | 31.9 °C | 130.81 mm |
| August | 19.7 °C | 31.6 °C | 109.47 mm |
| September | 16.2 °C | 29 °C | 105.16 mm |
| October | 9.4 °C | 23.3 °C | 99.57 mm |
| November | 3.5 °C | 16.8 °C | 104.14 mm |
| December | 0.6 °C | 11.7 °C | 151.64 mm |
| Annual | 9.6 °C | 22 °C | 1491.49 mm |
| Average First Frost Date | Nov. 1 - Nov. 10 |
| Average Last Frost Date | Mar. 21 - Mar. 31 |
| Average Days With Frost | 50-75 Days |
| Plant Hardiness Zone | Zone 8a : -12.2°C to -9.4°C |
| Plant Hardiness Zone - 2012 | Zone 7b : -15°C to -12.2°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |