Decatur, Texas has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 11.3 °C (low) to 23.7 °C (high). Annual precipitation averages 962.4 Millimeters. Decatur 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 | 0.1 °C | 12.7 °C | 51.31 mm |
| February | 1.9 °C | 14.7 °C | 62.23 mm |
| March | 6.3 °C | 19.2 °C | 87.88 mm |
| April | 10.4 °C | 23.4 °C | 82.04 mm |
| May | 15.7 °C | 27.2 °C | 120.65 mm |
| June | 20.3 °C | 31.8 °C | 108.97 mm |
| July | 22.5 °C | 34.4 °C | 60.2 mm |
| August | 22.1 °C | 34.6 °C | 64.52 mm |
| September | 17.9 °C | 30.5 °C | 89.66 mm |
| October | 11.8 °C | 24.7 °C | 102.87 mm |
| November | 5.8 °C | 18.4 °C | 67.06 mm |
| December | 0.8 °C | 13.3 °C | 65.02 mm |
| Annual | 11.3 °C | 23.7 °C | 962.41 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 | Normal |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |