Castroville, Texas has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 14.5 °C (low) to 27.4 °C (high). Annual precipitation averages 795 Millimeters. Castroville is located in USDA Plant Hardiness Zone 9a. The growing season typically runs from the last frost around Feb. 21 - Feb. 29 through the first frost around Nov. 21 - Nov. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 4.7 °C | 18 °C | 43.43 mm |
| February | 6.8 °C | 20.4 °C | 40.39 mm |
| March | 10.6 °C | 23.9 °C | 61.72 mm |
| April | 14.2 °C | 27.6 °C | 60.45 mm |
| May | 18.9 °C | 30.9 °C | 102.36 mm |
| June | 22.1 °C | 34 °C | 88.65 mm |
| July | 23 °C | 35.4 °C | 59.94 mm |
| August | 22.9 °C | 36.1 °C | 67.56 mm |
| September | 20.4 °C | 32.9 °C | 80.01 mm |
| October | 15.4 °C | 28.7 °C | 87.12 mm |
| November | 9.7 °C | 22.7 °C | 60.45 mm |
| December | 5.6 °C | 18.7 °C | 42.93 mm |
| Annual | 14.5 °C | 27.4 °C | 795.01 mm |
| Average First Frost Date | Nov. 21 - Nov. 30 |
| Average Last Frost Date | Feb. 21 - Feb. 29 |
| Average Days With Frost | 10-20 Days |
| Plant Hardiness Zone | Zone 9a : -6.7°C to -3.9°C |
| Plant Hardiness Zone - 2012 | Zone 8b : -9.4°C to -6.7°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |