Hamilton Branch, California has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 0.8 °C (low) to 16.7 °C (high). Annual precipitation averages 960.9 Millimeters. 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 | -5.2 °C | 6 °C | 167.39 mm |
| February | -4.8 °C | 7.9 °C | 155.19 mm |
| March | -3 °C | 10.8 °C | 142.75 mm |
| April | -1.1 °C | 13.7 °C | 78.74 mm |
| May | 2.5 °C | 19.1 °C | 48.51 mm |
| June | 5.8 °C | 24.7 °C | 21.34 mm |
| July | 8.8 °C | 29.6 °C | 8.64 mm |
| August | 8.1 °C | 29.1 °C | 7.62 mm |
| September | 5.1 °C | 25.6 °C | 10.16 mm |
| October | 0.7 °C | 18.4 °C | 48.01 mm |
| November | -2.7 °C | 10.4 °C | 96.77 mm |
| December | -5.2 °C | 5.5 °C | 175.77 mm |
| Annual | 0.8 °C | 16.7 °C | 960.89 mm |
| 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 : -17.8°C to -15°C |
| Plant Hardiness Zone - 2012 | Zone 7a : -17.8°C to -15°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |