Harriman, Tennessee has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 8.7 °C (low) to 21 °C (high). Annual precipitation averages 1515.6 Millimeters. Harriman 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 | -2.1 °C | 8.7 °C | 135.13 mm |
| February | -0.6 °C | 11.2 °C | 139.7 mm |
| March | 2.9 °C | 16.2 °C | 140.97 mm |
| April | 7.6 °C | 21.6 °C | 135.89 mm |
| May | 13 °C | 25.9 °C | 116.59 mm |
| June | 17.7 °C | 29.6 °C | 121.41 mm |
| July | 19.8 °C | 31.1 °C | 162.56 mm |
| August | 19.2 °C | 30.8 °C | 96.27 mm |
| September | 15.6 °C | 28.2 °C | 106.93 mm |
| October | 8.8 °C | 22.1 °C | 84.07 mm |
| November | 2.7 °C | 15.6 °C | 114.05 mm |
| December | -0.2 °C | 10.4 °C | 162.05 mm |
| Annual | 8.7 °C | 21 °C | 1515.62 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 | Severe Drought |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |