Slidell, Louisiana has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 59.3 °F (low) to 77.7 °F (high). Annual precipitation averages 65.6 Inches. Slidell is located in USDA Plant Hardiness Zone 9a. The growing season typically runs from the last frost around Feb. 21 - Feb. 29 through the first frost around Dec. 1 - Dec. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 42.0 °F | 61.7 °F | 5.78 in. |
| February | 45.5 °F | 65.3 °F | 4.58 in. |
| March | 51.7 °F | 71.4 °F | 5.14 in. |
| April | 58.4 °F | 77.3 °F | 5.41 in. |
| May | 66.4 °F | 84.2 °F | 5.53 in. |
| June | 72.7 °F | 89.1 °F | 6.15 in. |
| July | 74.4 °F | 90.7 °F | 7.8 in. |
| August | 74.3 °F | 90.9 °F | 7.05 in. |
| September | 70.6 °F | 87.6 °F | 4.95 in. |
| October | 60.8 °F | 80.1 °F | 4.04 in. |
| November | 50.6 °F | 70.7 °F | 4.19 in. |
| December | 44.5 °F | 63.7 °F | 5.01 in. |
| Annual | 59.3 °F | 77.7 °F | 65.63 in. |
| Average First Frost Date | Dec. 1 - Dec. 10 |
| Average Last Frost Date | Feb. 21 - Feb. 29 |
| Average Days With Frost | 10-20 Days |
| Plant Hardiness Zone | Zone 9a : 20°F to 25°F |
| Plant Hardiness Zone - 2012 | Zone 9a : 20°F to 25°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |