San Isidro, Texas has a Hot Semi-Arid Climate climate (Köppen classification: BSh). Average annual temperatures range from 17 °C (low) to 30.1 °C (high). Annual precipitation averages 571 Millimeters. San Isidro is located in USDA Plant Hardiness Zone 9b. The growing season typically runs from the last frost around Jan. 21 - Jan. 31 through the first frost around Dec. 21 - Dec. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 8.3 °C | 21.6 °C | 25.4 mm |
| February | 10.8 °C | 24.2 °C | 24.89 mm |
| March | 14.2 °C | 27.6 °C | 28.96 mm |
| April | 17.6 °C | 30.4 °C | 34.29 mm |
| May | 21.2 °C | 33.7 °C | 65.53 mm |
| June | 23.2 °C | 36.2 °C | 63.25 mm |
| July | 23.8 °C | 36.7 °C | 58.17 mm |
| August | 23.6 °C | 37.1 °C | 39.12 mm |
| September | 21.7 °C | 33.9 °C | 112.01 mm |
| October | 17.6 °C | 31.2 °C | 59.94 mm |
| November | 12.8 °C | 26.2 °C | 32.77 mm |
| December | 9.7 °C | 21.9 °C | 26.67 mm |
| Annual | 17 °C | 30.1 °C | 571 mm |
| Average First Frost Date | Dec. 21 - Dec. 31 |
| Average Last Frost Date | Jan. 21 - Jan. 31 |
| Average Days With Frost | Frost Rare |
| Plant Hardiness Zone | Zone 9b : -3.9°C to -1.1°C |
| Plant Hardiness Zone - 2012 | Zone 9b : -3.9°C to -1.1°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | BSh - Hot Semi-Arid Climate |