Portland, Texas has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 65.6 °F (low) to 79.1 °F (high). Annual precipitation averages 32.9 Inches. Portland is located in USDA Plant Hardiness Zone 10a.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 49.1 °F | 65.1 °F | 1.73 in. |
| February | 53.1 °F | 68.4 °F | 1.61 in. |
| March | 59.5 °F | 73.3 °F | 2.35 in. |
| April | 65.5 °F | 78.3 °F | 1.82 in. |
| May | 72.6 °F | 83.6 °F | 3.31 in. |
| June | 77.6 °F | 88.1 °F | 3.47 in. |
| July | 78.7 °F | 89.4 °F | 2.72 in. |
| August | 78.5 °F | 90.7 °F | 2.65 in. |
| September | 75.0 °F | 88.2 °F | 5.62 in. |
| October | 68.1 °F | 82.5 °F | 3.49 in. |
| November | 58.5 °F | 74.1 °F | 2.21 in. |
| December | 50.9 °F | 67.4 °F | 1.92 in. |
| Annual | 65.6 °F | 79.1 °F | 32.9 in. |
| Average First Frost Date | Frost Rare |
| Average Last Frost Date | |
| Average Days With Frost | Frost Rare |
| Plant Hardiness Zone | Zone 10a : 30°F to 25°F |
| Plant Hardiness Zone - 2012 | Zone 9b : 25°F to 20°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |