Glen Allan, Mississippi has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 12.4 °C (low) to 23.8 °C (high). Annual precipitation averages 1480.1 Millimeters. Glen Allan is located in USDA Plant Hardiness Zone 8b. The growing season typically runs from the last frost around Mar. 11 - Mar. 20 through the first frost around Nov. 1 - Nov. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 1.8 °C | 12 °C | 147.32 mm |
| February | 3.6 °C | 14.4 °C | 132.84 mm |
| March | 7.7 °C | 19.2 °C | 135.89 mm |
| April | 12.3 °C | 24.1 °C | 162.56 mm |
| May | 17.4 °C | 28.4 °C | 119.89 mm |
| June | 21.2 °C | 31.9 °C | 98.55 mm |
| July | 22.6 °C | 33.2 °C | 104.65 mm |
| August | 21.8 °C | 33.4 °C | 102.36 mm |
| September | 18.3 °C | 31 °C | 93.47 mm |
| October | 12 °C | 25.6 °C | 115.57 mm |
| November | 6.4 °C | 18.6 °C | 119.63 mm |
| December | 3.2 °C | 13.4 °C | 147.32 mm |
| Annual | 12.4 °C | 23.8 °C | 1480.05 mm |
| Average First Frost Date | Nov. 1 - Nov. 10 |
| Average Last Frost Date | Mar. 11 - Mar. 20 |
| Average Days With Frost | 40-50 Days |
| Plant Hardiness Zone | Zone 8b : -9.4°C to -6.7°C |
| Plant Hardiness Zone - 2012 | Zone 8a : -12.2°C to -9.4°C |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |