Grandfalls, Texas has a Hot Semi-Arid Climate climate (Köppen classification: BSh). Average annual temperatures range from 9.9 °C (low) to 27.7 °C (high). Annual precipitation averages 293.4 Millimeters. Grandfalls is located in USDA Plant Hardiness Zone 8a. 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 | -1.8 °C | 16.3 °C | 14.99 mm |
| February | 0.7 °C | 19.6 °C | 13.46 mm |
| March | 4.7 °C | 23.9 °C | 13.72 mm |
| April | 9.2 °C | 28.9 °C | 17.02 mm |
| May | 14.8 °C | 33.3 °C | 32.51 mm |
| June | 20.4 °C | 37.1 °C | 23.62 mm |
| July | 21.6 °C | 37.2 °C | 34.54 mm |
| August | 21 °C | 36.8 °C | 36.83 mm |
| September | 16.8 °C | 32.7 °C | 46.48 mm |
| October | 10.2 °C | 28.3 °C | 26.42 mm |
| November | 2.9 °C | 21.6 °C | 17.27 mm |
| December | -1.4 °C | 16.7 °C | 16.51 mm |
| Annual | 9.9 °C | 27.7 °C | 293.37 mm |
| Average First Frost Date | Nov. 11 - Nov. 20 |
| Average Last Frost Date | Mar. 11 - Mar. 20 |
| 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 | Normal |
| Köppen Climate Classification | BSh - Hot Semi-Arid Climate |