Harrison, Tennessee has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 9.6 °C (low) to 21.8 °C (high). Annual precipitation averages 1504.7 Millimeters. Harrison 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 | 9.9 °C | 145.8 mm |
| February | 0.6 °C | 12.4 °C | 135.64 mm |
| March | 4.2 °C | 17.2 °C | 142.24 mm |
| April | 8.8 °C | 22.3 °C | 122.68 mm |
| May | 14 °C | 26.4 °C | 109.22 mm |
| June | 18.6 °C | 30.1 °C | 116.84 mm |
| July | 20.7 °C | 31.8 °C | 138.18 mm |
| August | 20.1 °C | 31.6 °C | 103.89 mm |
| September | 16.5 °C | 28.7 °C | 124.46 mm |
| October | 9.5 °C | 22.9 °C | 85.85 mm |
| November | 3.1 °C | 16.4 °C | 125.48 mm |
| December | 0.5 °C | 11.4 °C | 154.43 mm |
| Annual | 9.6 °C | 21.8 °C | 1504.71 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 | Moderate Drought |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |