Grand Coteau, Louisiana has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 14.4 °C (low) to 25.8 °C (high). Annual precipitation averages 1640.6 Millimeters. Grand Coteau is located in USDA Plant Hardiness Zone 9a. The growing season typically runs from the last frost around Feb. 11 - Feb. 20 through the first frost around Nov. 21 - Nov. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 5.2 °C | 16.5 °C | 173.23 mm |
| February | 7.1 °C | 18.6 °C | 119.89 mm |
| March | 10.6 °C | 22.3 °C | 107.19 mm |
| April | 14.1 °C | 25.8 °C | 126.75 mm |
| May | 18.6 °C | 29.4 °C | 148.08 mm |
| June | 21.9 °C | 32.2 °C | 168.15 mm |
| July | 23 °C | 33 °C | 138.43 mm |
| August | 22.6 °C | 33.4 °C | 141.22 mm |
| September | 20.1 °C | 31.3 °C | 135.64 mm |
| October | 14.4 °C | 27.2 °C | 128.27 mm |
| November | 9.1 °C | 21.6 °C | 125.73 mm |
| December | 6.2 °C | 17.7 °C | 128.02 mm |
| Annual | 14.4 °C | 25.8 °C | 1640.6 mm |
| Average First Frost Date | Nov. 21 - Nov. 30 |
| Average Last Frost Date | Feb. 11 - Feb. 20 |
| Average Days With Frost | 10-20 Days |
| Plant Hardiness Zone | Zone 9a : -6.7°C to -3.9°C |
| Plant Hardiness Zone - 2012 | Zone 9a : -6.7°C to -3.9°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |