Sweeny, Texas has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 60.6 °F (low) to 79.5 °F (high). Annual precipitation averages 50.5 Inches. Sweeny is located in USDA Plant Hardiness Zone 9b.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 44.2 °F | 63.8 °F | 3.85 in. |
| February | 48.2 °F | 67.2 °F | 2.65 in. |
| March | 54.1 °F | 72.8 °F | 3.17 in. |
| April | 60.0 °F | 78.6 °F | 3.52 in. |
| May | 67.8 °F | 84.8 °F | 4.48 in. |
| June | 73.4 °F | 90.1 °F | 5.14 in. |
| July | 74.6 °F | 91.8 °F | 4.16 in. |
| August | 74.4 °F | 93.0 °F | 4.82 in. |
| September | 70.6 °F | 89.2 °F | 5.88 in. |
| October | 61.7 °F | 82.7 °F | 4.78 in. |
| November | 52.5 °F | 73.3 °F | 4.16 in. |
| December | 46.1 °F | 66.1 °F | 3.93 in. |
| Annual | 60.6 °F | 79.5 °F | 50.54 in. |
| Average First Frost Date | Frost Rare |
| Average Last Frost Date | |
| Average Days With Frost | Frost Rare |
| Plant Hardiness Zone | Zone 9b : 25°F to 20°F |
| Plant Hardiness Zone - 2012 | Zone 9a : 20°F to 25°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |