Mertzon, Texas has a Hot Semi-Arid Climate climate (Köppen classification: BSh). Average annual temperatures range from 51.3 °F (low) to 78.7 °F (high). Annual precipitation averages 19.8 Inches. Mertzon 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 | 31.7 °F | 59.1 °F | 0.92 in. |
| February | 35.3 °F | 63.9 °F | 1.36 in. |
| March | 42.9 °F | 71.1 °F | 1.54 in. |
| April | 49.9 °F | 80.5 °F | 1.52 in. |
| May | 60.3 °F | 87.9 °F | 2.16 in. |
| June | 67.7 °F | 93.4 °F | 2.42 in. |
| July | 70.0 °F | 95.6 °F | 1.58 in. |
| August | 69.2 °F | 95.4 °F | 1.94 in. |
| September | 62.2 °F | 88.5 °F | 2.41 in. |
| October | 52.1 °F | 79.8 °F | 1.91 in. |
| November | 41.1 °F | 68.1 °F | 1.17 in. |
| December | 33.0 °F | 60.5 °F | 0.88 in. |
| Annual | 51.3 °F | 78.7 °F | 19.81 in. |
| 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 : 10°F to 15°F |
| Plant Hardiness Zone - 2012 | Zone 8a : 10°F to 15°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | BSh - Hot Semi-Arid Climate |