Blackwell, Texas has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 10.4 °C (low) to 25.1 °C (high). Annual precipitation averages 553 Millimeters. Blackwell is located in USDA Plant Hardiness Zone 8a. 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 | -0.8 °C | 14.3 °C | 21.34 mm |
| February | 1.3 °C | 16.6 °C | 30.99 mm |
| March | 5.6 °C | 21 °C | 36.58 mm |
| April | 9.6 °C | 25.6 °C | 40.13 mm |
| May | 15.3 °C | 29.8 °C | 62.23 mm |
| June | 19.9 °C | 33.2 °C | 72.39 mm |
| July | 20.9 °C | 34.9 °C | 34.8 mm |
| August | 20.8 °C | 34.8 °C | 64.52 mm |
| September | 17.1 °C | 31.1 °C | 63.5 mm |
| October | 10.8 °C | 25.8 °C | 67.82 mm |
| November | 4.4 °C | 19.4 °C | 36.07 mm |
| December | 0.1 °C | 14.9 °C | 22.61 mm |
| Annual | 10.4 °C | 25.1 °C | 552.98 mm |
| Average First Frost Date | Nov. 1 - Nov. 10 |
| Average Last Frost Date | Mar. 21 - Mar. 31 |
| Average Days With Frost | 50-75 Days |
| Plant Hardiness Zone | Zone 8a : -12.2°C to -9.4°C |
| Plant Hardiness Zone - 2012 | Zone 8a : -12.2°C to -9.4°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |