Mertzon, Texas has a Hot Semi-Arid Climate climate (Köppen classification: BSh). Average annual temperatures range from 10.7 °C (low) to 25.9 °C (high). Annual precipitation averages 503.2 Millimeters. 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 | -0.2 °C | 15.1 °C | 23.37 mm |
| February | 1.8 °C | 17.7 °C | 34.54 mm |
| March | 6.1 °C | 21.7 °C | 39.12 mm |
| April | 9.9 °C | 26.9 °C | 38.61 mm |
| May | 15.7 °C | 31.1 °C | 54.86 mm |
| June | 19.8 °C | 34.1 °C | 61.47 mm |
| July | 21.1 °C | 35.3 °C | 40.13 mm |
| August | 20.7 °C | 35.2 °C | 49.28 mm |
| September | 16.8 °C | 31.4 °C | 61.21 mm |
| October | 11.2 °C | 26.6 °C | 48.51 mm |
| November | 5.1 °C | 20.1 °C | 29.72 mm |
| December | 0.6 °C | 15.8 °C | 22.35 mm |
| Annual | 10.7 °C | 25.9 °C | 503.17 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 | Normal |
| Köppen Climate Classification | BSh - Hot Semi-Arid Climate |