Portland, Tennessee has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 48 °F (low) to 67.9 °F (high). Annual precipitation averages 53.4 Inches. Portland 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 Nov. 1 - Nov. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 27.1 °F | 44.5 °F | 4.31 in. |
| February | 30.1 °F | 49.3 °F | 4.53 in. |
| March | 37.9 °F | 58.3 °F | 5.06 in. |
| April | 46.7 °F | 68.8 °F | 4.85 in. |
| May | 57.1 °F | 76.8 °F | 5.6 in. |
| June | 64.8 °F | 84.4 °F | 4.57 in. |
| July | 68.2 °F | 87.6 °F | 4.69 in. |
| August | 66.7 °F | 87.1 °F | 3.64 in. |
| September | 59.6 °F | 81.4 °F | 3.69 in. |
| October | 48.1 °F | 70.5 °F | 3.68 in. |
| November | 37.7 °F | 58.0 °F | 3.78 in. |
| December | 31.4 °F | 48.2 °F | 5.04 in. |
| Annual | 48 °F | 67.9 °F | 53.44 in. |
| Average First Frost Date | Nov. 1 - Nov. 10 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 7b : 5°F to 10°F |
| Plant Hardiness Zone - 2012 | Zone 7a : 0°F to 5°F |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |