Castaic, California has a Hot-Summer Mediterranean Climate climate (Köppen classification: Csa). Average annual temperatures range from 10.6 °C (low) to 25.6 °C (high). Annual precipitation averages 412.3 Millimeters. Castaic is located in USDA Plant Hardiness Zone 10a. The growing season typically runs from the last frost around Feb. 1 - Feb. 10 through the first frost around Dec. 21 - Dec. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 6.7 °C | 18.4 °C | 98.3 mm |
| February | 6.4 °C | 18.8 °C | 110.49 mm |
| March | 7.4 °C | 20.9 °C | 63.5 mm |
| April | 8.7 °C | 23.4 °C | 18.8 mm |
| May | 10.8 °C | 26.2 °C | 12.7 mm |
| June | 12.9 °C | 29.8 °C | 1.02 mm |
| July | 15.7 °C | 33.7 °C | 1.78 mm |
| August | 15.9 °C | 34.5 °C | 0.51 mm |
| September | 14.8 °C | 32.7 °C | 2.03 mm |
| October | 12.2 °C | 27.8 °C | 13.46 mm |
| November | 8.9 °C | 22.6 °C | 19.81 mm |
| December | 6.4 °C | 18.1 °C | 69.85 mm |
| Annual | 10.6 °C | 25.6 °C | 412.25 mm |
| Average First Frost Date | Dec. 21 - Dec. 31 |
| Average Last Frost Date | Feb. 1 - Feb. 10 |
| Average Days With Frost | 10-20 Days |
| Plant Hardiness Zone | Zone 10a : -1.1°C to 1.7°C |
| Plant Hardiness Zone - 2012 | Zone 9b : -3.9°C to -1.1°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Csa - Hot-Summer Mediterranean Climate |