Castella, California has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 6 °C (low) to 21.4 °C (high). Annual precipitation averages 1424.4 Millimeters. Castella is located in USDA Plant Hardiness Zone 8b. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 0.3 °C | 10.2 °C | 269.75 mm |
| February | 0.7 °C | 12.4 °C | 237.24 mm |
| March | 2 °C | 15.3 °C | 219.96 mm |
| April | 3.9 °C | 18.8 °C | 99.31 mm |
| May | 7.5 °C | 24.1 °C | 65.28 mm |
| June | 11.1 °C | 29.2 °C | 28.7 mm |
| July | 14.3 °C | 34.2 °C | 4.83 mm |
| August | 13.3 °C | 34.1 °C | 4.06 mm |
| September | 10.3 °C | 30.9 °C | 14.99 mm |
| October | 6.1 °C | 23.6 °C | 70.36 mm |
| November | 2.4 °C | 14.4 °C | 145.54 mm |
| December | 0.2 °C | 9.6 °C | 264.41 mm |
| Annual | 6 °C | 21.4 °C | 1424.43 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 8b : -9.4°C to -6.7°C |
| Plant Hardiness Zone - 2012 | Zone 8b : -9.4°C to -6.7°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |