Jefferson, Louisiana has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 16.9 °C (low) to 25.7 °C (high). Annual precipitation averages 1670.3 Millimeters. Jefferson is located in USDA Plant Hardiness Zone 9b.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 7.4 °C | 16.7 °C | 140.97 mm |
| February | 9.2 °C | 18.7 °C | 108.71 mm |
| March | 12.8 °C | 22.2 °C | 115.06 mm |
| April | 16.5 °C | 25.8 °C | 122.17 mm |
| May | 20.7 °C | 29.6 °C | 138.68 mm |
| June | 23.8 °C | 32.3 °C | 187.45 mm |
| July | 24.9 °C | 33.1 °C | 193.29 mm |
| August | 24.8 °C | 32.9 °C | 188.21 mm |
| September | 23.1 °C | 30.9 °C | 141.22 mm |
| October | 18.1 °C | 26.8 °C | 97.28 mm |
| November | 12.4 °C | 21.4 °C | 104.9 mm |
| December | 8.9 °C | 17.9 °C | 132.33 mm |
| Annual | 16.9 °C | 25.7 °C | 1670.27 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 |