San Juan, Texas has a Hot Semi-Arid Climate climate (Köppen classification: BSh). Average annual temperatures range from 64.5 °F (low) to 85.6 °F (high). Annual precipitation averages 22.3 Inches. San Juan is located in USDA Plant Hardiness Zone 10a.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 49.5 °F | 71.0 °F | 0.83 in. |
| February | 53.5 °F | 75.5 °F | 0.99 in. |
| March | 59.2 °F | 80.8 °F | 1.17 in. |
| April | 65.0 °F | 86.4 °F | 1.38 in. |
| May | 71.3 °F | 91.0 °F | 2.29 in. |
| June | 75.2 °F | 95.4 °F | 2.5 in. |
| July | 76.2 °F | 96.7 °F | 2.26 in. |
| August | 76.3 °F | 97.9 °F | 1.6 in. |
| September | 73.0 °F | 92.7 °F | 4.74 in. |
| October | 65.9 °F | 87.7 °F | 2.35 in. |
| November | 57.5 °F | 79.4 °F | 1.25 in. |
| December | 50.9 °F | 72.4 °F | 0.89 in. |
| Annual | 64.5 °F | 85.6 °F | 22.25 in. |
| Average First Frost Date | Frost Rare |
| Average Last Frost Date | |
| Average Days With Frost | Frost Free |
| Plant Hardiness Zone | Zone 10a : 30°F to 25°F |
| Plant Hardiness Zone - 2012 | Zone 9b : 25°F to 20°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | BSh - Hot Semi-Arid Climate |