Port Sulphur, Louisiana has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 17.3 °C (low) to 25 °C (high). Annual precipitation averages 1682.5 Millimeters. Port Sulphur is located in USDA Plant Hardiness Zone 9b.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 8.1 °C | 16.4 °C | 131.57 mm |
| February | 9.7 °C | 18.3 °C | 103.38 mm |
| March | 12.8 °C | 21.3 °C | 107.7 mm |
| April | 16.6 °C | 24.7 °C | 112.78 mm |
| May | 20.8 °C | 27.9 °C | 133.35 mm |
| June | 23.8 °C | 31.5 °C | 183.64 mm |
| July | 24.9 °C | 31.7 °C | 224.28 mm |
| August | 25 °C | 31.8 °C | 213.61 mm |
| September | 23.6 °C | 30.1 °C | 157.23 mm |
| October | 19.2 °C | 26.4 °C | 113.28 mm |
| November | 13.4 °C | 21.5 °C | 104.9 mm |
| December | 9.4 °C | 17.8 °C | 96.77 mm |
| Annual | 17.3 °C | 25 °C | 1682.49 mm |
| Average First Frost Date | Frost Rare |
| Average Last Frost Date | |
| Average Days With Frost | Frost Rare |
| Plant Hardiness Zone | Zone 9b : -3.9°C to -1.1°C |
| Plant Hardiness Zone - 2012 | Zone 9b : -3.9°C to -1.1°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |