Hornbrook, California has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 38.5 °F (low) to 68.2 °F (high). Annual precipitation averages 18.9 Inches. Hornbrook is located in USDA Plant Hardiness Zone 8a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 28.4 °F | 47.2 °F | 2.86 in. |
| February | 29.7 °F | 52.6 °F | 2.15 in. |
| March | 32.2 °F | 57.7 °F | 1.96 in. |
| April | 35.7 °F | 64.6 °F | 1.46 in. |
| May | 41.7 °F | 74.1 °F | 1.29 in. |
| June | 46.8 °F | 82.1 °F | 0.68 in. |
| July | 52.9 °F | 92.4 °F | 0.44 in. |
| August | 51.8 °F | 91.7 °F | 0.33 in. |
| September | 45.5 °F | 84.9 °F | 0.39 in. |
| October | 37.2 °F | 70.8 °F | 1.3 in. |
| November | 31.9 °F | 54.1 °F | 2.47 in. |
| December | 28.4 °F | 45.7 °F | 3.57 in. |
| Annual | 38.5 °F | 68.2 °F | 18.9 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 8a : 10°F to 15°F |
| Plant Hardiness Zone - 2012 | Zone 8a : 10°F to 15°F |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |