Port Isabel, Texas has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 68.6 °F (low) to 79.5 °F (high). Annual precipitation averages 26 Inches. Port Isabel is located in USDA Plant Hardiness Zone 10b.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 54.3 °F | 67.3 °F | 1.64 in. |
| February | 57.4 °F | 70.3 °F | 1.32 in. |
| March | 62.5 °F | 73.9 °F | 1.41 in. |
| April | 68.3 °F | 78.5 °F | 1.33 in. |
| May | 74.2 °F | 83.6 °F | 1.88 in. |
| June | 77.9 °F | 87.4 °F | 2.16 in. |
| July | 78.8 °F | 88.6 °F | 1.52 in. |
| August | 79.4 °F | 89.5 °F | 1.68 in. |
| September | 77.3 °F | 87.0 °F | 5.87 in. |
| October | 72.5 °F | 82.6 °F | 3.25 in. |
| November | 63.9 °F | 75.8 °F | 2.13 in. |
| December | 56.2 °F | 69.4 °F | 1.79 in. |
| Annual | 68.6 °F | 79.5 °F | 25.98 in. |
| Average First Frost Date | Frost Rare |
| Average Last Frost Date | |
| Average Days With Frost | Frost Free |
| Plant Hardiness Zone | Zone 10b : 35°F to 30°F |
| Plant Hardiness Zone - 2012 | Zone 10a : 30°F to 25°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |