Decatur, Mississippi has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 11.1 °C (low) to 24.4 °C (high). Annual precipitation averages 1494.5 Millimeters. Decatur is located in USDA Plant Hardiness Zone 8b. The growing season typically runs from the last frost around Mar. 21 - Mar. 31 through the first frost around Nov. 1 - Nov. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 1.3 °C | 13.8 °C | 147.32 mm |
| February | 3 °C | 16.4 °C | 132.59 mm |
| March | 6.6 °C | 20.6 °C | 145.54 mm |
| April | 10.4 °C | 24.5 °C | 156.21 mm |
| May | 15.2 °C | 28.4 °C | 106.93 mm |
| June | 19.4 °C | 32.1 °C | 115.32 mm |
| July | 21 °C | 33.1 °C | 128.02 mm |
| August | 20.4 °C | 33 °C | 122.43 mm |
| September | 17.4 °C | 30.8 °C | 90.17 mm |
| October | 10.7 °C | 25.6 °C | 92.96 mm |
| November | 4.9 °C | 19.5 °C | 119.38 mm |
| December | 2.5 °C | 15.1 °C | 137.67 mm |
| Annual | 11.1 °C | 24.4 °C | 1494.54 mm |
| Average First Frost Date | Nov. 1 - Nov. 10 |
| Average Last Frost Date | Mar. 21 - Mar. 31 |
| 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 | Normal |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |