Mer Rouge, Louisiana has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 11.7 °C (low) to 24.5 °C (high). Annual precipitation averages 1461 Millimeters. Mer Rouge is located in USDA Plant Hardiness Zone 8b. 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 | 1.4 °C | 13.3 °C | 141.73 mm |
| February | 3.2 °C | 15.8 °C | 131.06 mm |
| March | 7 °C | 20.1 °C | 141.48 mm |
| April | 11.2 °C | 24.6 °C | 155.19 mm |
| May | 16.3 °C | 28.7 °C | 125.73 mm |
| June | 20.5 °C | 32.3 °C | 99.82 mm |
| July | 22.1 °C | 33.8 °C | 101.09 mm |
| August | 21.5 °C | 34.1 °C | 102.11 mm |
| September | 17.6 °C | 31.4 °C | 90.68 mm |
| October | 11.1 °C | 26 °C | 112.27 mm |
| November | 5.9 °C | 19.2 °C | 118.87 mm |
| December | 2.6 °C | 14.6 °C | 140.97 mm |
| Annual | 11.7 °C | 24.5 °C | 1461 mm |
| Average First Frost Date | Nov. 11 - Nov. 20 |
| Average Last Frost Date | Mar. 1 - Mar. 10 |
| Average Days With Frost | 30-40 Days |
| Plant Hardiness Zone | Zone 8b : -9.4°C to -6.7°C |
| Plant Hardiness Zone - 2012 | Zone 8b : -9.4°C to -6.7°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |