Duncan, Mississippi has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 11.7 °C (low) to 22.6 °C (high). Annual precipitation averages 1404.9 Millimeters. Duncan 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. 11 - Nov. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 0.9 °C | 10.4 °C | 125.98 mm |
| February | 2.4 °C | 12.9 °C | 132.84 mm |
| March | 6.7 °C | 17.7 °C | 132.84 mm |
| April | 11.6 °C | 23 °C | 152.91 mm |
| May | 16.9 °C | 27.6 °C | 132.33 mm |
| June | 21 °C | 31.3 °C | 106.17 mm |
| July | 22.4 °C | 32.6 °C | 101.35 mm |
| August | 21.6 °C | 32.6 °C | 79.5 mm |
| September | 17.8 °C | 30.2 °C | 81.53 mm |
| October | 11.4 °C | 24.3 °C | 98.55 mm |
| November | 5.7 °C | 17.2 °C | 114.55 mm |
| December | 2.3 °C | 11.9 °C | 146.3 mm |
| Annual | 11.7 °C | 22.6 °C | 1404.85 mm |
| Average First Frost Date | Nov. 11 - Nov. 20 |
| 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 |