Simpson, Louisiana has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 13.4 °C (low) to 25.3 °C (high). Annual precipitation averages 1474.5 Millimeters. Simpson is located in USDA Plant Hardiness Zone 9a. The growing season typically runs from the last frost around Mar. 1 - Mar. 10 through the first frost around Nov. 11 - Nov. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 3.7 °C | 15.2 °C | 151.13 mm |
| February | 5.4 °C | 17.5 °C | 124.71 mm |
| March | 9.1 °C | 21.6 °C | 123.7 mm |
| April | 12.9 °C | 25.4 °C | 136.91 mm |
| May | 17.7 °C | 29.2 °C | 119.63 mm |
| June | 21.3 °C | 32.3 °C | 120.65 mm |
| July | 22.6 °C | 33.6 °C | 103.89 mm |
| August | 22.3 °C | 34 °C | 96.27 mm |
| September | 19.4 °C | 31.6 °C | 108.46 mm |
| October | 13.3 °C | 26.6 °C | 108.2 mm |
| November | 7.8 °C | 20.5 °C | 137.16 mm |
| December | 4.7 °C | 16.2 °C | 143.76 mm |
| Annual | 13.4 °C | 25.3 °C | 1474.47 mm |
| Average First Frost Date | Nov. 11 - Nov. 20 |
| Average Last Frost Date | Mar. 1 - Mar. 10 |
| Average Days With Frost | 20-30 Days |
| Plant Hardiness Zone | Zone 9a : -6.7°C to -3.9°C |
| Plant Hardiness Zone - 2012 | Zone 8b : -9.4°C to -6.7°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |