Hornbrook, California has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 3.6 °C (low) to 20.1 °C (high). Annual precipitation averages 480.1 Millimeters. 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 | -2 °C | 8.4 °C | 72.64 mm |
| February | -1.3 °C | 11.4 °C | 54.61 mm |
| March | 0.1 °C | 14.3 °C | 49.78 mm |
| April | 2.1 °C | 18.1 °C | 37.08 mm |
| May | 5.4 °C | 23.4 °C | 32.77 mm |
| June | 8.2 °C | 27.8 °C | 17.27 mm |
| July | 11.6 °C | 33.6 °C | 11.18 mm |
| August | 11 °C | 33.2 °C | 8.38 mm |
| September | 7.5 °C | 29.4 °C | 9.91 mm |
| October | 2.9 °C | 21.6 °C | 33.02 mm |
| November | -0.1 °C | 12.3 °C | 62.74 mm |
| December | -2 °C | 7.6 °C | 90.68 mm |
| Annual | 3.6 °C | 20.1 °C | 480.06 mm |
| 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 : -12.2°C to -9.4°C |
| Plant Hardiness Zone - 2012 | Zone 8a : -12.2°C to -9.4°C |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |