Castella, California has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 42.8 °F (low) to 70.5 °F (high). Annual precipitation averages 56.1 Inches. 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 | 32.5 °F | 50.4 °F | 10.62 in. |
| February | 33.2 °F | 54.4 °F | 9.34 in. |
| March | 35.6 °F | 59.6 °F | 8.66 in. |
| April | 39.0 °F | 65.8 °F | 3.91 in. |
| May | 45.5 °F | 75.4 °F | 2.57 in. |
| June | 51.9 °F | 84.6 °F | 1.13 in. |
| July | 57.8 °F | 93.6 °F | 0.19 in. |
| August | 55.9 °F | 93.3 °F | 0.16 in. |
| September | 50.6 °F | 87.7 °F | 0.59 in. |
| October | 43.0 °F | 74.5 °F | 2.77 in. |
| November | 36.4 °F | 58.0 °F | 5.73 in. |
| December | 32.3 °F | 49.2 °F | 10.41 in. |
| Annual | 42.8 °F | 70.5 °F | 56.08 in. |
| 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 : 15°F to 20°F |
| Plant Hardiness Zone - 2012 | Zone 8b : 15°F to 20°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |