Hamilton Branch, California has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 33.4 °F (low) to 62.1 °F (high). Annual precipitation averages 37.8 Inches. Hamilton Branch is located in USDA Plant Hardiness Zone 7a. The growing season typically runs from the last frost around May 21 - May 31 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 22.7 °F | 42.8 °F | 6.59 in. |
| February | 23.3 °F | 46.3 °F | 6.11 in. |
| March | 26.6 °F | 51.5 °F | 5.62 in. |
| April | 30.1 °F | 56.6 °F | 3.1 in. |
| May | 36.5 °F | 66.3 °F | 1.91 in. |
| June | 42.5 °F | 76.4 °F | 0.84 in. |
| July | 47.8 °F | 85.2 °F | 0.34 in. |
| August | 46.5 °F | 84.4 °F | 0.3 in. |
| September | 41.2 °F | 78.1 °F | 0.4 in. |
| October | 33.3 °F | 65.2 °F | 1.89 in. |
| November | 27.2 °F | 50.7 °F | 3.81 in. |
| December | 22.7 °F | 41.9 °F | 6.92 in. |
| Annual | 33.4 °F | 62.1 °F | 37.83 in. |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 21 - May 31 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 7a : 0°F to 5°F |
| Plant Hardiness Zone - 2012 | Zone 7a : 0°F to 5°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |